What Does an Assembler Do?

Translator for translating programs written in assembly language into equivalent machine language programs. The assembler inputs a source program written in assembly language and outputs an object program expressed in machine language. Assembly language is a machine-oriented language designed for a specific computer or computer family, and consists of assembly execution instructions and assembly pseudo-instructions. Although writing programs in assembly language is not as simple and intuitive as high-level programming languages, the compiled target programs occupy less memory, run more efficiently, and can directly reference various device resources of the computer. It is usually used to write core programs of the system, or to write program segments that require a large amount of running time and high real-time requirements.

Assembly execution instructions are symbolic representations of machine instructions, whose opcodes are represented by memory characters, and address codes are directly represented by labels, variable names, and constants. The assembly execution instructions are translated into machine instructions by the assembler, and there is basically a one-to-one correspondence between the two. Assembly directives, also known as assembly instructions, are used to provide the assembler with user-defined symbols, the type of data, the length of the data space, and

The prototype of the assembler was developed on the electronic discrete-time sequential automatic computer EDSAC. The characteristic of this system is that the instructions in the user program consist of a single-letter instruction code, a decimal address, and a terminating letter. The first assembler was the Symbol Optimized Assembler (SOAP) system, which was developed for the IBM650 computer in the mid-1950s. This computer uses a magnetic drum for

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Working process: input

The CPU is only responsible for calculations, and it is not intelligent. You enter an instruction, it runs once, then stops and waits for the next instruction.

These instructions are binary and are called opcodes. For example, the addition instruction is 00000011. The role of the compiler is to translate a program written in a high-level language into a series of opcodes.

To humans, binary programs are unreadable, and it is impossible to see what the machine does. In order to solve the problem of readability and occasional editing needs, assembly language was born.

Assembly language is the textual form of binary instructions, and there is a one-to-one correspondence with instructions. For example, the addition instruction 00000011 written in assembly language is ADD. As long as it is reduced to binary, the assembly language can be directly executed by the CPU, so it is the lowest level low-level language ^[1] .