THE Programming Language "C" Developed by Brian Kernighan and Dennis Ritchie of AT&T Bell Labs in 1972

In year 1983 the American National Standards Institute began the standardization process

In 1989 the International Standards Organization continued the standardization process

In 1990 a standard was finalized, known simply as “Standard C”

C can be thought of as a “high level assembler” Most popular programming language for writing system software

Focus on the procedural programming paradigm, with facilities for programming in a structured style

Low-level unchecked access to computer memory via the use of pointers


C language is the structured programming language because it has some standards.

Code re-usability means we can use the code from environment to other environment.

Built in type float, int etc expressions, operators.

Syntax for decision control.

It has some libraries which pre is defined.(preprocessors).

File organization (.c, .cpp etc).


C is a small , efficient ,powerful and flexible language

C is close to computer H/W (architecture).

C is standardized, making it more portable compare to other languages.

It contains libraries.

Many other languages borrow from syntax for ex: Java, java script, perl.

UNIX was written in C.


C is designed for professional users.

C was not able to automatic checking compare other languages.

C does not support modern concept like OOP’s and multi-threading.

Writing C Programs

A programmer uses a text editor to create or modify files containing C code.

Code is also known as source code.

A file containing source code is called a source file.

After a C source file has been created, the programmer must invoke the C compiler before the program can be executed (run)

Getting an executable program

The process of conversion from source code to machine executable code is a multi step process.

If there are no errors in the source code, the processes called compilation & linking produce an executable file

To execute the program, at the prompt, type < program >.exe


There are three popular steps used for conversion from .C to .exe

1) Preprocessing

2) Compilation

3) Linking


Performed by a program called the preprocessor

a) Modifies the source code (in RAM) according to preprocessor directives (preprocessor commands) embedded in the source code

b) Strips comments and white space from the code

c) The source code as stored on disk is not modified


Performed by a program called the compiler.

Checks for syntax errors and warnings

Translates the preprocessor-modified source code into object code (machine code).

Saves the object code to a disk file (.obj)

If any compiler errors are received, no object code file will be generated.

An object code file will be generated if only warnings, not errors, are received


Combines the program object code with other object code to produce the executable file.

a) The other object code can come from the

– Run-Time Library

– other libraries

– or object files that you have created.

b) Saves the executable code (.exe) to a disk file.

c) If any linker errors are received, no executable file is generated.

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