Chapter 1 Encoding and Transmission
Nyquist's theorem: R=2W*log2(N)
Manchester encoding is a bi-phase code
differential Manchester encoding: it flips when it encounters 0 and does not change when it encounters 1.
Manchester encoding: There is a level jump in each bit, which provides rich synchronization information. The comprehensive function encoding is used in applications where the speed is not very high. High Ethernet
The E1 frame is 8 bits, 32 channels, and is sent 8000 times per second, so 8*32*8000=2.048Mb/s. The
transmission rate of the E1 channel is 2.048Mb/s.
The transmission rate of each voice channel is 64kb/s.
Hamming code: m+k+1<2^k
E1-E5 has always been the data rate multiplied by 4.
T1-T5 T1 channel, the transmission rate is 1.544Mb/s
T2 channel, 4 T1 channels,
T3 channels, 7 T2 channels,
T4 channels, and 6 T3 channels
The HDLC protocol is a bit-oriented synchronous link control protocol that uses the 01111110 flag as the frame delimiter
2DPSK Each bit contains two cycles. If the carrier frequency is 2400Hz, the symbol rate is 1200 baud.
Delay:
For cable channel: tp=200km/(200km/ms)=10ms
For satellite channel: tp=270ms
Shannon theory calculation data rate:
C=W*log2(1+S/N)
db=10*lg(S/N)
Chapter 2: Network Architecture
FTP 21 TELENT 23 SNMT 25 DNS 53 TFTP 69 HTML 80 SNMP 161
Multicast address:
reserved D address 224.0.0.0-239.255.255.255
224.0.0.0-224.0.0.255 reserved multicast address (permanent group address) 224. 0.0.0 is reserved and not allocated
224.0.1.0-224.0.1.255 public group Broadcast address, used for Internet
224.0.2.0-238.255.255.255 User-available multicast address (temporary group address), network-wide range
239.0.0.0-239.255.255.255 Local management multicast address, specific local range valid
automatic dedicated IP address ：169.254.0.0-169.254.255.255
UDP header: source port, destination port, data length, checksum
POP3 protocol: The client agent and the server establish a TCP connection. This protocol is based on TCP port 110.
The host bits cannot be all 1 or 0
Internal private addresses:
10.0.0.0-10.255.255.255
172.16.0.0-172.31.255.255
192.168.0.0-192.168.255.255
IPV6 unicast address type: The
format prefix of the global unicast address 2000::/3
The format prefix of the link local address FE80::/12 The
format prefix of the site local address FEC0::/10
The global unicast address is equivalent to the IPV4 public network Address, allows aggregation of route prefixes, aggregation global unicast address format prefix: 001
link local address: communication between local nodes in stateless auto-configuration
Site-local address is similar to IPV4 private address. Will not be forwarded to other sites outside this site
MAC address:
6 bytes 48 bits
The minimum overhead of both the IP header and the TCP header is 20 bytes, and the Ethernet frame header and frame trailer total 18 bytes.
SMTP sends emails, running on TCP, port 25
Chapter 3 Network Classification
The standard protocol of the limited LAN at the MAC layer is CSMA/CD (Carrier Sense Multipoint Access/Collision Detection)
802.11 CSMA/CA (Carrier Sense Multipoint Access/Collision Avoidance)
CSMA/CD has high transmission medium utilization and high collision probability
1. Non-persistent listening algorithm: idle, sending, busy, wait N before listening. Reduce the probability of conflict, reduce channel utilization, and increase transmission delay.
2. I-persistent monitoring algorithm: idle, sending, busy, continue monitoring. It is helpful to seize the channel, reduce the idle time of the channel, and easily cause conflicts.
3. P-persistent listening algorithm: idle, send with probability P, busy, continue to listen. Effectively balance conflicts and channel utilization.
CSMA/CD uses the listening-to-change detection method.
The longest time it takes to detect conflicts is twice the network propagation delay.
Ethernet can connect up to 4 repeaters.
The transmission delay is <2 times the propagation delay. Delay 2S/0.7C+2tPHY+8tR
100BASE-T
is a local area network standard operating at 100Mbps, known as Fast Ethernet, using UTP (Unshielded Twisted Pair) copper cables
stipulating a distance of no more than 100 meters from the transceiver to the hub
802.11 2.4GHz ISM expansion communication technology 1MB/S 2MB/S
802.11B 2.4GHz ISM CCK technology 11MB/S
802.11a 5GHz U-Nii OFDM modulation technology 54MB/S
802.11g 2.4GHz ISM OFDM modulation technology 54MB/S
802.11n 6 6 00MB /s is backward compatible with abg, and both frequency bands can be supported
The original IEEE802.11 encryption method is Limited Equivalence Protocol (WEP).
802.11i defines a new key exchange protocol TKIP, adopts the advanced encryption standard AES, and uses 802.1x to implement access control.
The air interface standard for wireless access systems proposed by IEEE802.16: WiMAX
global microwave interconnection access, also called 802.16 wireless metropolitan area network, with data transmission up to 50km, QOS guarantee, high transmission rate, and rich services
Frame Relay FR
is divided into Permanent Virtual Circuit (PVC) and Switched Virtual Circuit (SVC).
Frame Relay is simpler than HDLC. It only does error detection and does not retransmit. There is no sliding window flow control mechanism, only congestion control, and the complex Error detection is handed over to higher-level
connection-oriented services, flow control, and traffic shaping technology.
Frame Relay virtual circuit identifier: DLCI
DLCI: Data link connection identifier, the value that identifies the PVC or SVC.
CIR: Committed Information Rate
LMI: Frame Relay Local Management interface, signaling standard between routers and Frame Relay switches, provides Frame Relay management mechanism
VPI: virtual path of ATM
The access layer implements user access control
, the aggregation layer: route selection between VLANs, packet filtering, and multicast management. The
core switching layer: link redundancy, route redundancy, VLAN trunking, and load balancing
provide high-speed connections between different areas. optimal transmission path
IEEE802.3 Ethernet frame length: the length from the destination address to the checksum
ADSL access:
PC: ADSL MODEM, splitter, home junction box, telephone line, DSL access multiplexer (DSLAM) connected to ATM or IP network
voice line: splitter, home junction box, telephone line, DSL connection Input multiplexer (DSLAM) access telephone switch
WPA wifi protection, a subset of 802.11i
ADSL VDSL (Very High Data Rate Digital Subscriber Line) Asymmetric transmission
SDSL Single pair digital subscriber
HDSL High data rate data subscriber
PPPoE allows an Ethernet host to connect to a remote access hub through a simple bridge device. ADSL uses the PPPoE protocol
IEEE802.ae 10 Gigabit Ethernet physical standard gets rid of the restriction that Ethernet can only be used in local area networks and can be used in metropolitan area networks and wide area networks.
Wireless network spread spectrum technology:
Each signal bit can be transmitted using N chip bits.
Technologies to reduce blocking probability include: direct sequence spread spectrum (DS), frequency hopping (FH), time hopping (TH), linear frequency modulation (Chirp) )
The wireless sensor network technology used in the Internet of Things is 802.15.3ZigBee Piconet
X.25 (packet switching technology), Frame Relay, and ATM (Asynchronous Transfer Mode) all require the establishment of virtual circuits
Chapter 4: Network interconnection technology
BGP transport protocol TCP port number 17 Supports CIDR (Classless Inter-Domain Routing)
routing updates only send incremental routes, rich route filtering and routing policies
BGP4 introduction mechanism supports route aggregation, including AS path aggregation, using hop-by-hop routing Publish a list of reachable ASs
ACL protocol is TCP or UDP
standard access control 1-99
extended access control 100-199 2000-2699
eq gt lt neq log
The console port uses a dedicated configuration cable to directly connect to the computer serial port, and uses a terminal emulation program for local configuration. The
default data rate of the router console port is 9600b/s.
vtp pruning is a switch configuration command, VTP pruning. Reduce the amount of unnecessary information such as broadcast, multicast, unicast, reserved bandwidth, etc. on the trunk port
Broadcast multi-access network (broadcast multi-access) such as ethernet, token ring FDDI
non-broadcast multi-access network (none broadcast multi-access NBMA) such as frame relay x.25
point-to-point network such as PPP, HDLC
point-to-multipoint network such as RARP protocol network
The difference between RIP 1 and 2 versions, three improvements:
1. Adopts a triggered update mechanism to accelerate routing convergence
2. Supports variable length subnet mask and classless inter-domain routing (VLSM, CIDR)
3. Use experience Hash passwords to limit the dissemination of routing information
4. Multicast instead of broadcast
5. Support authentication
OSPF area:
standard area
backbone area
stub area
complete stub area
incomplete stub area
MPLS: (Multi-Label Forwarding Protocol)
A fast packet switching and routing system that provides destinations for network data traffic. The ability to route, forward, and switch is
independent of layer 2 and 3 protocols such as ATM and IP. It maps IP addresses to Labels with fixed length for different packet forwarding and packet switching capabilities
Loose source routing: IP packets must pass through the router specified by the source site
RIP protocol prevents routing loops:
split horizon, route poisoning, suppression time, triggered updates, setting maximum metric value
show ip route can view the routing table information of the local router and view the routing information. The
show command can be executed in user mode and privileged mode.
The factory serial port encapsulation protocol of the router is HDLC (Advanced Data Link Control), which can support multi-point addressing.
You can change the protocol to PPP or Frame Relay yourself.
Link state routing protocols (SPF, OSPF) do not exchange routing tables with each other.
Triggered updates occur when the network changes and send periodic update link state notifications.
Benefits of using routers for LAN segmentation: isolation of broadcast domains, routing and addressing
OSPF 32-bit identification ID, 0-65535, 0 is the backbone area
The destination address matches the network entry with the longest subnet mask.
RSVP: The recipient applies for resource reservation. This application is one-way.
During the transition period between IPV4 and IPV6:
1. Dual protocol stack
2. Tunnel technology
3. NAT-PT translation technology
Chapter 5: Cybersecurity
Public key encryption is also called asymmetric key encryption.
The form of a public key is a digital certificate.
Commonly used symmetric encryption algorithms: DES (American Data Encryption Standard), RC-5, IDEA
Asymmetric: RSA, MD5, elgamal, backpack algorithm, Rabin, DH, DSA, ECC (elliptic curve encryption algorithm)
AES Advanced Encryption Standard
3DES is A shared secret key algorithm
Diffie-Hellman key exchange algorithm
PGP encryption algorithm: email encryption
Message digest algorithm MD5: output is 128-bit
SHA-1 output: 160-bit
SET: standard for secure online credit card payment
IPsec: a security protocol based on the IP layer, used in VPN
Security association triplet in IPsec: security parameter index SPI, target IP address, security protocol
Function of digital signature: ensure the integrity of information transmission, identity authentication of the sender, and prevent denial of transactions.
Digital signature algorithm: hash, DSS, RSA.
Design of digital signature: the sender cannot deny it, and the receiver can verify but cannot fabricate it. or tamper with
Private key for decryption and signing
Public key for encryption and authentication
Secure Hash Algorithm SHA-1:
A message with a maximum length of no more than 264 bits is input, generates a 160-bit message digest output, and 512 blocks are used to process the input
Prevent replay attacks:
one-time keys, sequence numbers, timestamps
The Kerberos system uses one-time keys and timestamps.
In the Kerberos authentication system, users first apply for an initial ticket from the authentication server AS, and then obtain the session key from the ticket granting service period TGS.
Kerberos is used to ensure security in a distributed network environment. A central authentication server provides user-to-server and server-to-user authentication services, using DES encryption technology.
IPsec key management is implemented using the IKE (Internet Key Exchange Protocol) mechanism. IKE solves the problem of securely establishing or updating shared keys in an insecure network environment.
80: Default port of web service
8080: Web service in LAN
445, 193: LAN shared folder, printer
443: Default port of SSL protocol
Database disaster recovery belongs to system security and application security
DES algorithm key length 64bit
Triple DES algorithm key length 128bit
Authentication methods supported by the IIS service, only basic authentication uses clear text
VPN tunnel protocol: IPsec L2TP GRE PPTP L2F etc.
GRE IPsec belongs to the third layer tunneling protocol
L2TP PPTP L2F belongs to the second layer tunneling protocol
L2TP protocol encapsulation: IP UDP L2TP PPP PPP payload
IEEE802.11i defines a new encryption protocol CCMP based on AES
HTTP Hypertext Transfer Protocol, information plain text transmission
HTTPS SSL encrypted transmission protocol with security, the security mechanism is at the transport layer port 443
S-HTTP Secure Hypertext Transfer Protocol, a protocol for secure information communication, the security mechanism is at the application layer
Virus:
CIH: malignant, destroys computer hardware
Happy Hour: VB source program virus, specially infects htm, html vbs, sap
Panda Burning Incense: variant worm virus, downloaded file infection, destroys computer system, Program
X undercover: Trojan horse, infects smartphones
Worms, CIH viruses, and macro viruses are all stand-alone viruses. Trojan is a Trojan horse virus that enables remote attacks through the network.
Macro viruses: infect MS office system files.
PKI (public key infrastructure)
IETF divides the intrusion system into 4 components:
event generator, event analyzer, corresponding unit, and event database
Windows server 2003 system builds a domain environment:
communication group, security group (local domain group, global group, universal group)
Chapter 6 Network Software System
To change the default FTP port number in Linux system: you can modify /etc/vsftpd/vsftpd.conf
/etc/hostname contains the host name of the system, including the complete domain name
/etc/hostname.interface file names the network card
/ect/hosts host name and IP configuration file
/etc/resolv.conf sets the DNS of the host
/etc/networks Use Name the subnet
/etc/gateways routing table file
/etc/shadow
/etc/passwd shadow is the shadow file of passwd, corresponding to each other. Shadow includes users and encrypted passwords, user expiration dates, etc.
Commonly used configurations of web servers under Linux:
/etc/inetd.conf TCPIP service configuration file, add or delete a service
/etc/lilo.conf Loader configuration file, configure Linux boot parameters
/etc/httpd/conf/httpd.conf Configuration server Port number used
/etc/httpd/conf/access.conf Security and user access related settings
/etc/resolve.conf DNS domain name resolution configuration file
Nameserver DNS server IP address
Domain Local domain name
Search Domain name search list
Sortlist Sort the returned domain names
The host directory is the root of the virtual directory. Only the www service supports virtual servers.
FTP related commands:
dir: You can specify the list directory to be viewed to display the remote directory file and subdirectory list
! dir: Display file information in the current directory of the client
rpm: Manage various software packages
IN: Create a file in another location File link
SNMP:
UDP port 162 of the management process, port 161 of the agent process.
get-request, get-next-request, set-request are all sent by the management to the agent.
get-response trap is sent by the agent to the management
. In SNMP network management, one agent can be managed by multiple network managers. Workstation management, starting from V2, gateway workstations can also manage each other.
SNMP trap packets use port 162, and other types are UDP port 161.
SNMP service program:
snmp.exe snmptrap.exe
When configuring the SNMP service, the current login user needs to belong to the super management group (administrator member)
SNMPc support: FTP SMTP WEB TELNET
The first character of the linux ls-al command - represents a normal file, d represents a directory, l represents a connection file, and b represents a device file.
Windows system:
regedit command enters the registry editor
cmd enters the DOS command line
mmc opens the windows management console
tracert (trace route) is a route tracing utility used to confirm the path taken by IP datagrams to access the target. -d specifies not to resolve the IP address to the host name route
print to view the local routing table
Cat more and less can view the file content. cat outputs all the file content at one time. more paging view less cursor movement.
IIS: web ftp smtp nntp is a set of integrated software in IIS and does not provide POP3 services.
xinetd is a daemon process. Linux centrally monitors all the listening ports of some network-related services (ftp, http) by xinetd.
After receiving the request, it temporarily starts the corresponding service and transfers the corresponding port to the corresponding service.
route add 10.41.0.0 mask 255.255.0.0 10.27.0.1 metric 7
The DHCP client can obtain from the DHCP server: DHCP server IP address, DNS server IP address, default gateway IP address
SMTP port number: 25
The main resource records in the DNS server:
A: Domain name to IP address mapping
PTR: IP address to domain name mapping
MX: Mail server and its priority
CNAM: Alias
NS: Authorization server for the region
nslookup Diagnoses information about the Domain Name System infrastructure and views IP addresses of DNS servers
tracert Traceroute utility used to determine the path taken by an IP datagram to reach a destination
arp Displays and modifies values in the arp cache
arp -s ip address physical address: Staticly bind an IP and MAC mapping record,
display and modify the local address cache resolution table for static arp. The address resolution table is a cache memory that records the data link layer address, usually the mapping of Ethernet MAC address to IP address.
ipconfig TCPIP configuration setting value, refresh DHCP DNS setting
ipconfig/all displays the TCPIP configuration of all network cards
netstat provided by windows Network management commands, monitor TCPIP, display routing tables, actual network connections, and status information of each network interface device
Windows Server 2003 Active Directory manages network resources. Active Directory needs to be installed in the NTFS area.
/proc is mainly used to store process and system information
. It saves all detailed information of the current system, including processes, file systems, hardware, etc.
Some parameters in the system can be modified instantly through /proc.
Common Linux commands:
cd Change the current working directory
pwd Display the current directory
mkdir Create a new directory
ls View directory, file
cp Copy
rm Delete
mv Move
cat The first line displays the file content
tac The last line
more Displays page by page
less Display files Allow users
to shutdown forward and backward , close system
logout, log out,
grep, search for the specified string in the specified file,
chmod, change the permissions of the file.
Linux configuration file
/root directory
/bin Places various command programs and different shells used when the OS is running
/boot Places files that must be read during startup, system kernel, configuration files
/dev Peripheral device code files
/etc System settings , management related files
/etc/rc.d Shutdown script file
/home Home directory of all accounts
/lib Common library file
/mnt Default place for placing CDs and floppy disks
/root Administrator's private directory
/usr subdirectory, use To store system commands and programs
/var to store various temporary files and log files when the system is running
/sbin to store the programs executed when the system is started.
Network availability refers to the percentage of time the network is available to users
The difference between RMON and SNMP:
RMON provides management information for the entire subnet, while the SNMP management information base only contains the management information of local devices. The RMON
monitoring system has two parts: the detector and management station
management information base are part of MIB-2, and the monitor Statistics and analysis can be performed on each group
GRUB can boot both Linux and windows systems.
LILO can only boot Linux.
APIPA (Automatic Private IP Addressing) 169.254.0.1-169.254.255.254
Chapter 7 Network Communication Equipment
(The knowledge points are too detailed, so just give up. Chapter 7 of the real test usually only has one multiple-choice question, so there is no need to prepare carefully, just look at previous years' questions)
Chapter 8 Intellectual Property
Copyright can be divided into personal rights and property rights.
Personal rights are divided into: publication, signature, modification, and protection of the integrity of the work.
Property rights are divided into: reproduction, distribution, rental, exhibition, performance, screening, broadcasting, information network dissemination, filming, adaptation, translation, and compilation.
Chapter 9 Reliability and System Performance Evaluation
(Basically not tested in the real questions)
Chapter 10 Storage System
The conversion between the main memory unit address and the cache unit address is completed by hardware.
Virtual memory:
It is usually divided into multiple physical memory fragments, some of which are temporarily stored on external disk storage, and data are exchanged when needed.
Virtual memory consists of two levels of main memory and auxiliary memory.
Memory Classification:
Location: Memory Outer Village
Material: Magnetic Memory, Semiconductor, Optical
Working Mode: Read/Write, Read-Only
Access Mode: Address Access, Content Access Associative Memory is Content Access Addressing
Mode: Random, Sequential, Direct
Access mode read-write device data block tag access characteristics represent
sequential access shared unspecified linear tape
direct access shared data blocks, each unique tag can be directly moved to a specific data block disk
random access each addressable unit dedicated There is a unique identifier for each addressable unit. Access the data unit at any time. Main memory
associative access. Each addressable unit is unique. Each addressable unit has a unique identifier. Select the read and write point cache based on the content.
RAID technology has the highest disk capacity utilization: RAID0
RAID0: two or more disk drives, each disk is divided into different blocks, interleaved access, and parallel transmission.
Distribute data on different drives to increase transfer speed, balance drive load
No mirror disk, no error control
RAID1: Disk mirroring function 50%
RAID3: Parity check complete fault tolerance 75%
Open system storage methods:
built-in storage and external storage
External storage: direct-attached storage (DAS), networked storage (network access storage NAS, storage area storage SAN)
IR (instruction register) instruction register stores the instructions to be executed
Chapter 11 Operating System
windows2003 secure login: ctrl+alt+del
In operating system file management, file directories are used to organize and manage information in external memory. The
data structure of the management file is called a file control block (FCB), and the ordered collection of file control blocks is called a file directory.
Three basic states of operating system processes: ready, running, blocked
Interrupt vector:
The entry address of the interrupt service program that can be provided
refers to the data stored in the memory when an interrupt occurs and pointing to the address of the interrupt handler. Each interrupt vector occupies one word. The low byte is the interrupt number and the high byte is the routine. The offset address of the program
uses the stack to protect breakpoints and scenes:
protecting breakpoints means putting CS (segment address) and IP (offset) on the stack
DMA (Direct Memory Access)
uses a DMA Controller (DMAC) to control and manage data transfers. DMAC and CPU share the data bus and have the ability to access memory independently in
three ways:
1. Pause the CPU to hand over control until the DMA operation is completed
2. Cycle stealing mode temporarily abandons the bus when the CPU is idle and inserts a DMA cycle
3. Sharing mode The CPU does not use the system bus, and the DMAC performs DMA transfers.
Time slice rotation method:
number of users n, time slice q, system response time for each Tonghu: (n-1)*q+q=n*q
Chapter 12 Basic knowledge of system development and operation
Several popular development methods:
Structured development method
Data structure-oriented software development method: Jackson
Problem-oriented analysis method
Prototyping method
Object-oriented software development method: Booch Coad OMT
Several connections between UML entities:
dependency relationship,
generalization relationship
, association relationship (aggregation relationship, combination relationship)
, implementation relationship,
generalization relationship, and can also represent the special/general relationship that exists between two types of things.
Software risk includes two characteristics: uncertainty and loss.
Regression testing: Testing after a change has been made to the software to detect other errors that may have been caused by the change
White box testing: called structural testing. Commonly used techniques to
design test cases based on the internal structure and logic of the program involve different coverage standards. Test data is determined according to the specified coverage standards during testing.
Software design: abstraction, modularity, information hiding, and module independence
Software life cycle model:
Waterfall model requires clear requirements.
V model is an evolutionary model of the waterfall model. The evolutionary model associates testing and analysis with design. The
prototype model is a model that quickly builds a runnable prototype system based on feedback during the operation. The improvement
is suitable for situations where there is a lack of accurate understanding of software requirements.
The spiral model is combined with waterfall and evolution, and the risk analysis
fountain model is added
. Incremental model iteration, each increment releases an operational product, flexible personnel allocation, and can quickly construct runnable methods.
Reliability of the software product:
number of potential errors, location of potential errors, how the software product is used
Coupling:
from low to high non-direct coupling data coupling tag coupling control coupling external coupling public coupling content coupling
content coupling: one module directly modifies or operates the data of another module, or directly accesses another module
Methods for project estimation:
expert judgment, heuristic methods, machine learning methods
Chapter 13 Computer Hardware Structure
Program counter (PC):
A register in the CPU that stores the address of the next instruction to be executed.
Accumulation register (AC):
referred to as the accumulator. When the arithmetic logic unit (ALU) performs arithmetic or logical operations, it provides the ALU with an Workspace for transferring and staging user data
ALU:
The execution unit of the CPU, mainly responsible for the operation
program status register (PSW):
part of the controller, which stores various status information that reflects the current instruction execution structure and stores control information.
Address register: stores the address of the memory unit currently accessed by the CPU.
Calculator memory is generally divided into:
Static data area Code area Stack area Heap area Stack
area: The compiler automatically allocates and releases local variables allocated for running functions, function parameters, return data, return addresses, etc.
The operation mode is similar to the stack area in the data structure : the programmer allocates and releases it. If the programmer does not release it, the OS reclaims
the global area (static area): stores global variables, static data, and constants; the system releases
the program code after the program ends. Area: stores the binary code of the function body
The computer must perform an order operation before adding or subtracting floating point numbers. The order code of x is greater than the order code of Y. Y should be expanded to be the same as
The interrupt control method spends more CPU time processing interrupts, and the increased number of interrupts leads to data loss. I/O devices are suitable for transferring data using DMA with less CPU intervention.
The processor is mainly composed of a processor, a memory and a bus, including
a data bus, an address bus, and a control bus. The
component-level internal bus within the chip (system bus) and the external bus (communication bus)
CPU:
The control center of the computer, mainly composed of arithmetic units, controllers, register groups, internal buses and other components
Controller: program counter, instruction register, instruction decoder, timing generator, operation controller The controller
must not only ensure The normal execution of instructions must also be able to handle abnormal events.
The program counter (PC) is a special register with two functions: registering information and counting.
Internal bus: transmitting data, data address, control signal
Register:
scattered in the controller and arithmetic unit.
Program counter: stores the address of the next instruction.
Instruction register: stores the opcode to be executed by the central processor.
Flag register: records whether the arithmetic unit overflows, the result is 0 and other abnormal situations.
Data register: Stores operands, operation results, and intermediate results of operations.
Address register: stores the address of the memory unit currently accessed by the CPU.
Computer instructions:
including operation codes and address codes.
In order to analyze and execute an instruction, they should be stored in the instruction register.
The complement of a positive number is the same as the original code. The complement of a negative number is the absolute value. The complement of
a positive the same as its original code and complement. The complement of a negative number is its complement + 1.
The input/output control methods for data transmission between the computer host and peripherals include program control method, interrupt method, and DMA
Addressing mode:
How to provide operands or provide operand addresses.
Different addressing modes can be used to shorten the instruction length, expand the addressing space, and improve programming flexibility.
Immediate addressing 45 in MOV R1 #45
direct addressing Register Addressing R1 Register
in MOV R1 #45 Indirect Addressing Indirect Addressing Relative Addressing Indexed Addressing
Computer main memory:
consists of memory banks, addressing systems, memory data registers, reading and writing systems and control circuits. The
addressing system is the address selection mechanism for reading and writing information, including memory address register (MAR) and address decoding. device
Chapter 14 Computer English
The main thing is that it is not difficult to accumulate and understand the language.