1_introduction to c programming

8/2/2019 1_Introduction to C Programming

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Introduction to C programming

The C programing language was designed byDennis Ritchie at Bell laborataries in early1970s.

It was developed in conjunction with thedevelopment of UNIX .


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C : charecteristics

C takes middle way between a low levelassembly language

Direct access to memory layout throughpointer manipulation

Concise syntax , small set of keywords

And a high level programming language like

java Block structures

Some encpsulation of code (throughfunctions)


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Elements of a C program

C development environment includes

A set of standard libraries and their headerfiles

Application source and its header files

Compiler to convert the source to object for apaticular platfrom

Linker to resolve external references andproduce executable module


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User program structure

There must be one main funtion whereexecution begins when program is run.

This function is called the main

Int main (void)

{

.....................

}

Additional local functions and variables


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A simple C program

Program to display hello on in the console

#include

int main(void)

{

printf(hello\n);

}

The program created using any editor software

Eg gedit


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gedit

Start editing / typing the program by opening anew c file

Command gedit program_name

Eg gedit hello.c

After typing in the program save the program

The file hello.c Is called source which contains

the source code


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Compiling the program

After writing the source code we have toinvoke the compiler before running theprogram

Gcc compiler

Gcc program_name

Eg gcc hello.c or cc hello.c

The output file created is a.out

To run the out put file ./a.out

To redirect the output file from a.out

Gcc -o hello hello.c

Now the executable is hello instead of a.out


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Basic parts of the program #include

This includes header file stdio.h where all thestandard input output functions are defined

Function prototypes , datatypes, macros ,

inline functions and common definitions areincluded in header files.

Preprocessor insert this common definitionsto source files


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Preprocessor directive

Statements starting with # in the fisrt column iscalled preprocessor directive

#include directs preprocessor to include a

copy of the specified file

#define defines a macro. The preprocessorreplaces macro with original code whereverit is called.


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main()

Main is the main function of execution

When a program is made to run the main isexecuted

Subsequent functions are called from the mainfunction

Code of execution of main function as well assubfunctions are included in curlly brackets.


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Reserved Words (Keywords)

Keywords are that which have specialmeaning in C language

An identifier cannot have the same spellingand case as a C keyword

Eg int

main

char ..etc...


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Comments

Cooments are used to document the code

It is sequence of characters beginning with aforward slash asterisk combination (/*) andends with (*/)

Compiler consider it a s a single whitespaceand ignores

Single line comments can be made by //

A good programmers document his codewhile coding itself


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Identifiers

Identifiers or symbols are the names suppliedfor variables, types, functions, and labels inprogram.

Identifier names must differ in spelling andcase from any keywords


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Standard input and output

#include

int main()

{int a, b;

printf("enter twonumbers\n");

scanf("%d%d\n",&a,&b);printf(%d%d\n,a,b);

return 0

}


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Standard output function is printf

Standard output function is scanf

Their prototype is declared in stdio.h

1_introduction to c programming

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