Introduction To Compiler Design, What is Compiler, Preprocessor, Assembler, Interpreter, Advantages of Compiler, Loader and Link-Editor

Introduction To The Compiler Design

What is Compiler?

-A compiler is a special program that translates the source code of a programming language into 

machine code, bytecode, or another programming language. The source code is usually written in 

a high-level human-readable language, such as Java or C++.

The computer is an intelligent combination of software and hardware. Hardware is simply a piece 

of mechanical equipment and its functions are being compiled by the relevant software. The 

hardware considers instructions as electronic charge, which is equivalent to the binary language in 

software programming. The binary language has only 0s and 1s. To enlighten, the hardware code 

has to be written in binary format, which is just a series of 0s and 1s. Writing such code would be an 

inconvenient and complicated task for computer programmers, so we write programs in a high-level language, which is convenient for us to comprehend and memorize. These programs are then 

fed into a series of devices and operating system (OS) components to obtain the desired code that 

can be used by the machine. This is known as a language processing system.

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Preprocessor

-The preprocessor includes all header files and also evaluates whether a macro(A macro is a piece 

of code that is given a name. Whenever the name is used, it is replaced by the contents of the 

macro by an interpreter or compiler. The purpose of macros is either to automate the frequency 

used for sequences or to enable more powerful abstraction) is included. It takes source code as 

input and produces modified source code as output. The preprocessor is also known as a macro 

evaluator, processing is optional that is if any language that does not support #include and macros 

processing is not required.

Compiler

- Compiler is a translator program that translates a program written in (HLL) the

source program and translates it to an equivalent program in (MLL) the target program. An 

important part of a compiler is the error that is displayed to the programmer.

The execution of a program written in the HLL programming language basically consists of two 

parts. the source program must first be compiled into an object program. The result object 

program is then loaded into an executed memory.

Assembler

- Programmers found it difficult to write or read programs in machine language.

They begin to use a mnemonic (symbols) for each machine instruction, which they would later use 

translate into machine language.

Such a mnemonic machine language is now called assembly language.

Programs known as assemblers were written to automate the translation of assembly language into machine language.

The input to an assembly program is called a source program, and the output is a machine language 

translation (object program).

Interpreter

-An interpreter is a program that appears to execute a source program as if it 

were machine language

Languages such as BASIC, SNOBOL, and LISP can be translated using interpreters. JAVA also uses 

an interpreter. The process of interpretation can be carried out in the following phases.

1. Lexical analysis
2. Syntax analysis
3. Semantic analysis
4. Direct Execution

Advantages

- Modification of the user program can be easily performed and implemented as execution proceeds.

The object type denoting multiple can change dynamically.

Debugging a program and finding errors is a simplified task for a program used for interpretation.

The language interpreter makes it machine independent.

Disadvantages

-The Program execution is slower.

Memory consumption is more.

Loader and Link-Editor

- Once the assembler processes an object program, that program must be placed in memory and 

executed. The assembler could put the object program directly into memory and transfer control to it.

Thus causing the program to be executed in machine language. This would waste the kernel by leaving 

the assembler in memory while the user program was running. Also, the programmer would have to re-translate his program with each execution, thus wasting translation time. To overcome these problems 

of wasted translation time and memory. System programmers developed another component called a 

loader "A loader is a program that places programs in memory and prepares them for execution."

It would be more efficient if the subroutines could be translated into object form, and the loader 

could be "relocated" directly behind the user program. The task of adjusting programs so that 

they are not placed in arbitrary central locations is called relocation. Relocation chargers 

perform four functions.