2019-2020-1 20175204 "Information security system design basis" the second week of learning summary
learning target
1. important role in understanding binary computer
2. The master application boolean operation in C language
3. understanding signed integer, unsigned integers, floating point representation of
the importance of understanding complement 4.
5. C Language can be avoided overflow, data type conversion traps may lead to vulnerabilities and
6. the further understanding of the "information bits = + context"
Learning content summary
Highlights:
- Digital three kinds:
1. No symbols: based on the conventional binary notation, it represents a number greater than or equal to zero.
2. Complement: that the most common way of signed integer.
3. Float: two base-expressed in scientific notation version of real numbers.
4. Why would the vulnerability?
Because of loopholes in computing microseconds details computer arithmetic triggered.
- Conversion hex:
Note that for a binary intermediate result to get a better
- byte order and word:
word size: nominal length of one word indicating the data size of integers and pointers. Word to determine the most important system parameter is the maximum size of the virtual address space. A word length of w bits on the machine, the virtual address range is 0 ~ 2 ^ w-1, to access up to 2 ^ w bytes.
For multi-byte program object across the need to establish two rules:
little-endian: high high low low
big endian: small end and an opposite method. Becomes visible that the byte order of three ways: between different types of machines when transmitting binary data over a network, the network coding applications must adhere to the rules of byte order of established; disassembler use, with integers problems storage byte order byte sequence data; when written to circumvent the normal type system program.
- logic operations:
logical AND (&&) in case of 0 is 0;
logical OR (||) is the case of a 1;
a logic 0 to a non-case, the case 1 is 0;
- Bit operations:
Bitwise AND (&) Every case of binary 0 is 0;
Bitwise OR (|) Every case of binary 1 to 1;
Bitwise XOR (^) ^ 0 ^ 0 = 0, 0 1 = 1,1 ^ 1,1 ^ 0 = 1 = 0;
bitwise (~) invert each bit binary;
- integer arithmetic:
1. adding the unsigned
2's complement adder
3. unsigned multiply
two numbers x, y and multiplying the x, y is the number of bits w, the number of bits of the result is 2w.
4. complement multiplication
with the unsigned multiplication.
- Float:
1.IEEE representation as: V = (-1) * M * 2 ^ S ^ E
2. Symbols: s- symbol 0 is positive, 1 negative
3. mantissa: M is a binary fraction
4. order: E is the effect of floating-point data is weighted, the weights is a power of 2 E
- textbook learning and problem-solving process:
-1 questions:. Linux c programming "stdio.h: No such file or directory."
APT-GET install Build sudo-Essential ( https://blog.csdn.net/sean_y/article/details/3629028 )