What is the difference between assembly language and c language?

What is the difference between assembly language and c language? The following article will introduce to you the difference between assembly language and c language. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

What is c language:

C language is a general computer programming language and is widely used. The design goal of the C language is to provide a programming language that can be easily compiled, handle low-level memory, generate a small amount of machine code, and can run without any runtime environment support; although the C language provides many low-level processing functions, However, it still maintains good cross-platform characteristics. C language programs written in a standard specification can be compiled on many computer platforms, including some embedded processors (single chip microcomputer or MCU) and supercomputers and other operating platforms.

What is assembly language:

Assembly language (assembly language) is a programming language used for electronic computers, microprocessors, microcontrollers or other programmable devices. Low-level language, also known as symbolic language. In assembly language, mnemonics are used to replace the opcodes of machine instructions, and address symbols (Symbol) or labels are used to replace the addresses of instructions or operands. In different devices, assembly language corresponds to different machine language instruction sets, which are converted into machine instructions through the assembly process. Generally speaking, a specific assembly language and a specific machine language instruction set have a one-to-one correspondence and cannot be directly transplanted between different platforms.

Many assemblers provide additional support mechanisms for program development, assembly control, and auxiliary debugging. Some assembly language programming tools often provide macros, which are also called macro assemblers.

Assembly language is not as widely used in programming as most other programming languages. In today's practical applications, it is usually used in low-level, hardware operations and demanding program optimization situations. Assembly language is required for drivers, embedded operating systems, and real-time running programs.

The difference between C language and assembly language:

Assembly language: high efficiency, stronger controllability of hardware, small size, difficult to maintain, and portability Very poor

C language: relatively low efficiency, poor hardware controllability, large object code size, easy to maintain, and good portability

Assembly language has high operating efficiency Reasons:

1. Assembly language is essentially a mnemonic for machine language. The CPU can only run the instruction set it supports, and each instruction in these instruction sets is a sequence of binary numbers, that is, an ordered combination of "0" and "1"; The combination is not convenient for programmers to remember, so there are mnemonics such as "MOV A 0x40". Therefore, compiling assembly language into machine language executable by the CPU only requires a translation action. After writing a program in C language, a compiler needs to be used to compile the C language into machine language corresponding to the corresponding CPU instruction set. Assembly language and machine language have a one-to-one correspondence. But what about C language? Of course it's not such a good thing. The syntax of C language is fixed. When a program written in C language is compiled into machine language instructions that the CPU can understand, there is no one-to-one correspondence. Therefore, compilation rules are required, so the running efficiency is lower. It can also be said that C language is a language for programmers, while assembly language is a language directly for the CPU.

2. Assembly is a language that directly faces the CPU. As long as it is within the scope supported by the instruction set, assembly language can directly and flexibly manage every byte including special function registers, general registers, and storage units. , even every bit. The C language is also very powerful in its use and management of memory, but after all, it is still subject to syntax. To give the simplest example, there is no variable type corresponding to three bytes or five bytes in C language, either int type or long type, so each application must be a fixed number of bytes, which will inevitably cause memory usage. waste. Most assembly languages ​​do not have such syntax at all. With the help of pseudo-instructions (which actually only improve readability), assembly language programs can use variables of any number of bytes. Of course, processing them is much more troublesome than C language. In the end, it is still spliced ​​byte by byte, but writing a program in C language is easy. Don't worry about it, the compiler will eventually take care of it. The price of ease is waste. Inefficient memory usage will also affect the overall efficiency of the entire program. ??

Different applicable occasions of C language and assembly

1: If there are only simpler logical operations, logical algorithms, and simple operations, using assembly will result in more accurate results code, but it can also be done in c.

2: If there are complex operations, floating point operations, non-linear equations, etc., assembly is very difficult. As a high-level language, C language is concise and compact, and uses flexible syntax mechanisms to write complex programs. Much easier.

3: The assembly syntax of each processor is mostly different. If you only use assembly, the scalability and portability are very poor. Using C will be much better.

4: To initialize the hardware, use assembly language.

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