Since the advent of the first electronic computer, human communication and the machine has become a major research software engineers and computer practitioners, more efficient and simple programming language has become the new darling of the software engineers, with the rapid development of computers, hardware upgrade computer speed faster and faster, the requirements of increasingly stringent programming language. In the past few decades, the programming language has made great progress so far has been the advent of the fourth generation language. A large number of programming languages in order to meet programming requirements and software capabilities in different fields, experienced been modified, substituted, such as the development process, eventually evolved into now diversified programming language.
The first generation of machine-oriented machine language
concepts
computer is represented by a binary code to identify and directly executed by a machine a set of instructions. It is the designer of a computer given by the computer hardware structure of a computer operating functions.
Characteristics
(1) a machine language instruction is a statement, which is a set of meaningful binary code, the basic format instructions such as operation code field and an address code field, wherein the operation code indicates the nature of the operation and function of the instruction, the address code is given the address operand or operand.
(2) for the machine: the machine language for general computer for different models are different, the portability is poor, poor reusability. Each machine instructions, which represent the format and meaning of the code is mandatory, so called machine-oriented language, also called machine language.
For example, a computer word length is 16 bits, i.e. there is a binary number 16 instructions or other information. 1 0 and 16 can be composed of a variety of permutations, through a line into electrical signals, a computer to execute various operations.
The instruction is 1,011,011,000,000,000 certain computer, allows the computer once it represents the addition operation; 1011010100000000 represents the instruction for a subtraction operation. Their front operation code eight, then eight address code represents. Two instructions can be seen from the above, they are only in the opcode from the left side of bit 0 and bit 6 of 7 different. Such models may comprise 256 (= 2 8 power) different instructions.
(. 3) CPU, registers, memory, integrated hardware has a corresponding set of instructions, for example, called instruction of the CPU CPU machine language, machine language programmed, is the selection of a suitable instruction cpu command from a practical system, the composition a series of instructions ;;
example:
a, examples of the instruction portion
0000 representative of load (the lOAD)
0001 representing the Memory (the SET)
B, part of the sample register
0000 on behalf of register a
0001 on behalf of the register B
Example C, most of the memory
000000000000 representative of memory address is 0
000000000001 representative of the address of the memory 1
000 000 001 000 16 representative of the address of the memory
100 billion on behalf of the memory address is 2 ^ 11
D, integration Examples
0000,0000,000000001000 Representative LOADA, 16
0000,0000,000000000001 representatives loadb,. 1
0000,0001,000000001000 representatives STOREA, 16
0000,0001,000000000001 representatives STOREB,. 1
(. 4) can be read poor
The second generation of assembly language for a machine
concept
is the low-level language computer, a microprocessor, microcontroller or other programmable device for. In assembly language, machine code mnemonic instead of the operation instruction, with the address of the symbol number instead of address operations, also known as symbolic language.
Characteristics
(1) for the machine: the different devices, the assembly language instruction corresponds to a different set of machine language, into machine instructions through the assembly process. Specific assembly language and machine language instruction set specific one to one, not directly portable across different platforms.
(2) high efficiency, it is usually used in applications where the underlying hardware and operating demanding applications optimized, such as the driver, and real-time embedded operating system to run the program;
(3) simplicity and readability than the machine language good, for example: addition and subtraction on the "ADD" representative of digital logic, "MOV" represent the data transfer
(4) the machine does not recognize the need for the assembler language compiler into binary characters can be recognized by the computer; selected compiler It depends on the type of the target processor and platform specific
Example: Most are based on the 8086/8088 assembly language, different chips have some extended instructions.
The third-generation high-level language, process-oriented
The concept of
language, also known as process-oriented structured programming language. In the process-oriented programming, the problem is seen as a series of tasks to be done, the function is used to accomplish these tasks, focus on problem-solving focus function.
(1) Process-oriented processing tasks, regardless of the hardware configuration, but the process-oriented compiler language program into machine language programs with computer hardware-related
(2) sentence close to the natural expression
For example: C language
The fourth-generation object-oriented language
object-oriented is a real world understanding and abstract way, is a product of the development of computer programming technology to a certain stage. Object-oriented with respect to the process-oriented in terms of object-oriented approach, the relevant data and methods to look at the organization as a whole, to system modeling from a higher level, closer to the natural mode of operation of things.
Such as C ++, Java, Python
Fifth generation language natural language
concept
Knowledge is also known as artificial intelligence language or languages, the goal is the closest programming language the language of everyday life, it is mainly used in the field of artificial intelligence, to help people write reasoning, deduction program.
For artificial intelligence techniques to solve problems, often can not put all knowledge is embodied in a fixed program. Usually we need to build a knowledge base (containing facts and inference rules), a program to determine their own actions according to the environmental problem and enter information, and given to be solved, so it is reasoning in a guided environment modes. This method has great flexibility, the ability to dialogue, there are self-explanatory and learning ability. Fifth generation language has not yet appeared in the true sense