渥瑞达 Linux Unix下C语言软件开发视频教程 笔记3

Chapter 1 Getting Started

1.ASIMPLE EXAMPLE

This program prints out the message “Thisis a C program”

Example1:

#include <stdio.h>   int main() {          printf(  "This is a C Program\n" );                   return  0; }

Every C program contains a function calledmain , This is the start point of the program.

#include<stdio.h> allows the programto interact with the screen, keyboard and file system of your computer. Youwill find it at the beginning of almost every C program.

Main() declares the start of the function. Whilethe two curly brackets show the start and finish of the function.

Printf(“This is a C program\n”)

Prints the words on the screen . The textto be printed is enclosed in double quotes, The \n at the end of the text tellsthe program to print a newline as part of the output.

C is case sensitive, that is, it recognizesa lower case letter and it’s upper case equivalent as being different.

 

 

Compilingin Linux

Gcc is the compiler from Gnu

$ gcc hello.c

$ gcc –o sample hello.c

The compilation will proceed silently, andmake an executable file called a.out

 

Runningin Linux

./a.out

 

Result:

This is a C program

 

 

2.Comments

Emample2:

#include <stdio.h>   int main() {          int  Counter=0; /* Initalise Counter */          /*  a comment */          /*           *Another comment           */          return  0; }

A comment starts with a /*and ends with*/

 

Summary:

The basic structure of a one-functionprogram i:

#include <stdio.h> /*************************************************  *...Heading comments...*  *************************************************/ /*Data declaractions*/   int main() {          /*...Executable  statements...*/          return  0; }