Difference between revisions of "C-and-C-Plus-Plus/C2/First-C-Program/English"

Learning Objectives

To write a simple C program

To compile it

To execute it

We will also explain some common errors and their solutions.

System Requirements

Ubuntu operating system version 11.10

and gcc Compiler 4.6.1 on Ubuntu

Prerequisites

You should be familiar with Ubuntu Operating System

an Editor

Some editors are vim and gedit

I will use gedit in this tutorial

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Open the terminal using Ctrl + Alt + T simultaneously

Open the terminal by pressing Ctrl, Alt and T keys simultaneously

gedit talk.c &

“gedit” space “talk” dot “c” space [ampersand] “&”

We use ampersand (&) to free up the prompt

“My first C program”.

Comments are used to understand the flow of program

It is useful for documentation

It gives us information about the program

The double slash is called as single line comment.

#include <>

#include <stdio.h>

“stdio” dot”.” “h”

A program must contain this header file when it uses standard input/output functions.

and press Enter .

int main()

It denotes that the execution of the program begins from this line

The opening bracket and the closing bracket is called as parenthesis.

It returns a value of type integer.

There should NOT be more than one main function

Otherwise the compiler cannot locate the beginning of the program

The empty pair of parentheses indicates that main has no arguments

The concept of arguments will be discussed in detail in the upcoming tutorials.

{

The opening curly bracket marks the beginning of the function main.

}

The closing curly bracket indicates the end of the function main.

Move the cursor one line up

press Enter twice, and then move the cursor one line up

It also helps to locate errors faster

So let us give three space here

printf()

printf is a standard C function to print the output on the terminal

printf("Talk To a Teacher\n");

within double quotes,

Anything within the double quotes in the printf statement will be pritned on the terminal.

Type

“Talk To a Teacher backslash n”

As a result, after execution of the printf function,

the cursor moves to a new line

Hence, type it at the end of this line.

Semicolon acts as a statement terminator.

give three space here

An integer has to be returned for this function

because the function type is int

The return statement marks the end of executable statements

We will learn more about the returned values in another tutorial.

It is a good habit to save files frequently

This will protect you from sudden power failures

It will also be useful in case the applications were to crash.

gcc talk.c -o myoutput

Please open the terminal

Type “gcc” space “talk.c” space hyphen “-o” space “myoutput”

talk.c is the filename

on compilation gcc creates an executable

-o myoutput says that the executable should go to the file myoutput

Press Enter.

By typing ls -lrt, we can see that myoutput is the last file to be created

type dot slash “./myoutput”

and press Enter.

Thus after the return statement nothing will be executed

Let us try it out.

type printf("Welcome \n");

Type ./myoutput

gcc talk.c -o myoutput

./myoutput.

That is what I did now

We see that the statements after return are not executed

above return 0;

Let us write the 'Welcome' statement above the return statement

and press Enter.

We see that the second printf statement also has been executed

Let's switch to the editor

<stdio.h>

<stdio.h>

I will retain rest of the code as it is

Switch to the terminal

Let us go to the terminal

and press Enter.

We see that

There is a fatal error in our talk.c file at line no.1 and column no.18

The compiler cannot find a header file with the name “stdioh”

hence the compilation is terminated.

Reinsert the dot “.”

It is working.

Let us switch back to the editor

printf("Talk To a Teacher\n")

Switch to the terminal.

“clear” command.

using command that we have used before.

And press Enter.

So it will search for it at the end of the line

and also at the beginning of the next line.

This is line 5

Recall that the compiler also gives the error message on line 5.

Put semicolon back in original location

It is working

Assignment

Write a program to print "Welcome to the World of C"

See what happens if we do not write “\n” in the printf statement.

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http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

It summarises the Spoken Tutorial project

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Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of India

More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro

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