The

Basic Building Blocks Of The C Programming


You have seen the basic structure of a C program, so it will be easy to understand other basic building blocks of the C programming language.

Tokens in C

A C program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following C statement consists of five tokens −

printf("Hello, World! \n");
The individual tokens are −
printf
(
   "Hello, World! \n"
)
;

Semicolons

In a C program, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity.

Given below are two different statements −

printf("Hello, World! \n");
return 0;

Comments

Comments are like helping text in your C program and they are ignored by the compiler. They start with /* and terminate with the characters */ as shown below −

/* my first program in C */

You cannot have comments within comments and they do not occur within a string or character literals.

Identifiers

A C identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter A to Z, a to z, or an underscore '_' followed by zero or more letters, underscores, and digits (0 to 9).

C does not allow punctuation characters such as @, $, and % within identifiers. C is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in C. Here are some examples of acceptable identifiers −

mohd zara abc move_name a_123
myname50 _temp j a23b9 retVal

Keywords

The following list shows the reserved words in C. These reserved words may not be used as constants or variables or any other identifier names.


Whitespace in C

A line containing only whitespace, possibly with a comment, is known as a blank line, and a C compiler totally ignores it.

Whitespace is the term used in C to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement −

int age;

there must be at least one whitespace character (usually a space) between int and age for the compiler to be able to distinguish them. On the other hand, in the following statement −

fruit = apples + oranges; // get the total fruit

no whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish to increase readability.

Hello World Example


A C program basically consists of the following parts −

• Preprocessor Commands
• Functions
• Variables
• Statements & Expressions
• Comments

Let us look at a simple code that would print the words "Hello World" −

INPUT

#include <stdio.h>
void main {
   /* my first program in C */
   printf("Hello, World! \n");
   getch;
}

Let us take a look at the various parts of the above program −

• The first line of the program #include <stdio.h> is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.
• The next line int main() is the main function where the program execution begins.
• The next line /*...*/ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program.
• The next line printf(...) is another function available in C which causes the message "Hello, World!" to be displayed on the screen.
• The next line return 0; terminates the main() function and returns the value 0.

Compile and Execute C Program

Let us see how to save the source code in a file, and how to compile and run it. Following are the simple steps −

• Open a text editor and add the above-mentioned code.
• Save the file as hello.c
• Open a command prompt and go to the directory where you have saved the file.
• Type gcc hello.c and press enter to compile your code.
• If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file.
• Now, type a.out to execute your program.
• You will see the output "Hello World" printed on the screen.

OUTPUT

Hello, World

Applications of C Programming


C was initially used for system development work, particularly the programs that make-up the operating system. C was adopted as a system development language because it produces code that runs nearly as fast as the code written in assembly language. Some examples of the use of C are -

• Operating Systems
• Language Compilers
• Assemblers
• Text Editors
• Print Spoolers
• Network Drivers
• Modern Programs
• Databases
• Language Interpreters
• Utilities

Audience

This tutorial is designed for software programmers with a need to understand the C programming language starting from scratch. This C tutorial will give you enough understanding on C programming language from where you can take yourself to higher level of expertise.

Prerequisites

Before proceeding with this tutorial, you should have a basic understanding of Computer Programming terminologies. A basic understanding of any of the programming languages will help you in understanding the C programming concepts and move fast on the learning track.

What Is C Programming


C programming is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis M. Ritchie at the Bell Telephone Laboratories to develop the UNIX operating system. C is the most widely used computer language. It keeps fluctuating at number one scale of popularity along with Java programming language, which is also equally popular and most widely used among modern software programmers.


Why to Learn C Programming?

C programming language is a MUST for students and working professionals to become a great Software Engineer specially when they are working in Software Development Domain. I will list down some of the key advantages of learning C Programming:

• Easy to learn
• Structured language
• It produces efficient programs
• It can handle low-level activities
• It can be compiled on a variety of computer platforms
• Facts about C
• C was invented to write an operating system called UNIX.
• C is a successor of B language which was introduced around the early 1970s.
• The language was formalized in 1988 by the American National Standard Institute (ANSI).
• The UNIX OS was totally written in C.
• Today C is the most widely used and popular System Programming Language.
• Most of the state-of-the-art software have been implemented using C.
• Today's most popular Linux OS and RDBMS MySQL have been written in C.

INPUT

#include <stdio.h>
#include <graphics.h>
#include <conio.h>
#include <dos.h>
int main() {
int gd = DETECT, gm;
int i, maxx, midy;
initgraph(&gd, &gm, "C:\\TURBOC3\\BGI");
maxx = getmaxx();
midy = getmaxy()/2;
for (i=0; i < maxx-150; i=i+5) {
cleardevice();
setcolor(WHITE);
line(0, midy + 37, maxx, midy + 37);
setcolor(YELLOW);
setfillstyle(SOLID_FILL, RED);
line(i, midy + 23, i, midy);
line(i, midy, 40 + i, midy - 20);
line(40 + i, midy - 20, 80 + i, midy - 20);
line(80 + i, midy - 20, 100 + i, midy);
line(100 + i, midy, 120 + i, midy);
line(120 + i, midy, 120 + i, midy + 23);
line(0 + i, midy + 23, 18 + i, midy + 23);
arc(30 + i, midy + 23, 0, 180, 12);
line(42 + i, midy + 23, 78 + i, midy + 23);
arc(90 + i, midy + 23, 0, 180, 12);
line(102 + i, midy + 23, 120 + i, midy + 23);
line(28 + i, midy, 43 + i, midy - 15);
line(43 + i, midy - 15, 57 + i, midy - 15);
line(57 + i, midy - 15, 57 + i, midy);
line(57 + i, midy, 28 + i, midy);
line(62 + i, midy - 15, 77 + i, midy - 15);
line(77 + i, midy - 15, 92 + i, midy);
line(92 + i, midy, 62 + i, midy);
line(62 + i, midy, 62 + i, midy - 15);
floodfill(5 + i, midy + 22, YELLOW);
setcolor(BLUE);
setfillstyle(SOLID_FILL, DARKGRAY);

circle(30 + i, midy + 25, 9);
circle(90 + i, midy + 25, 9);
floodfill(30 + i, midy + 25, BLUE);
floodfill(90 + i, midy + 25, BLUE);
/* Add delay of 0.1 milli seconds */
delay(100);
}
getch();
closegraph();
return 0;
}

OUTPUT

INPUT

#include <graphics.h>
#include <stdio.h>
#include <math.h>
#include <dos.h>
void main( )
{
float x,y,x1,y1,x2,y2,dx,dy,step;
int i,gd=DETECT,gm;
initgraph(&gd,&gm,"c:\\turboc3\\bgi");
printf("Enter the value of x1 and y1 : ");
scanf("%f%f",&x1,&y1);
printf("Enter the value of x2 and y2: ");
scanf("%f%f",&x2,&y2);
dx=abs(x2-x1);
dy=abs(y2-y1);
if(dx>=dy)
step=dx;
else
step=dy;
dx=dx/step;
dy=dy/step;
x=x1;
y=y1;
i=1;
while(i<=step)
{
putpixel(x,y,5);
x=x+dx;
y=y+dy;
i=i+1;
delay(100);
}
getch();
closegraph();
}

OUTPUT

INPUT

#include<stdio.h>
#include<graphics.h>

void drawline(int x0, int y0, int x1, int y1)
{
int dx, dy, p, x, y;

dx=x1-x0;
dy=y1-y0;

x=x0;
y=y0;

p=2*dy-dx;

while(x<x1)
{
if(p>=0)
{
putpixel(x,y,7);
y=y+1;
p=p+2*dy-2*dx;
}
else
{
putpixel(x,y,7);
p=p+2*dy;
}
x=x+1;
}
}

int main()
{
int gdriver=DETECT, gmode, error, x0, y0, x1, y1;
initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi");

printf("Enter co-ordinates of first point: ");
scanf("%d%d", &x0, &y0);

printf("Enter co-ordinates of second point: ");
scanf("%d%d", &x1, &y1);
drawline(x0, y0, x1, y1);

getch();
}


OUTPUT

1.  Scaling about the origin followed by translation.
2.  Scaling with reference to an arbitrary point.
3. Reflect about the line y = mx + c.

INPUT

#include <stdio.h>
#include <graphics.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>

void reset (int h[][2])
{
int val[9][2] = {
{ 50, 50 },{ 75, 50 },{ 75, 75 },{ 100, 75 },
{ 100, 50 },{ 125, 50 },{ 125, 100 },{ 87, 125 },{ 50, 100 }
};
int i;
for (i=0; i<9; i++)
{
h[i][0] = val[i][0]-50;
h[i][1] = val[i][1]-50;
}
}
void draw (int h[][2])
{
int i;
setlinestyle (DOTTED_LINE, 0, 1);
line (320, 0, 320, 480);
line (0, 240, 640, 240);
setlinestyle (SOLID_LINE, 0, 1);
for (i=0; i<8; i++)
line (320+h[i][0], 240-h[i][1], 320+h[i+1][0], 240-h[i+1][1]);
line (320+h[0][0], 240-h[0][1], 320+h[8][0], 240-h[8][1]);
}
void rotate (int h[][2], float angle)
{
int i;
for (i=0; i<9; i++)
{
int xnew, ynew;
xnew = h[i][0] * cos (angle) - h[i][1] * sin (angle);
ynew = h[i][0] * sin (angle) + h[i][1] * cos (angle);
h[i][0] = xnew; h[i][1] = ynew;
}
}
void scale (int h[][2], int sx, int sy)
{
int i;
for (i=0; i<9; i++)
{
h[i][0] *= sx;
h[i][1] *= sy;
}
}
void translate (int h[][2], int dx, int dy)
{
int i;
for (i=0; i<9; i++)
{
h[i][0] += dx;
h[i][1] += dy;
}
}
void reflect (int h[][2], int m, int c)
{
int i;
float angle;
for (i=0; i<9; i++)
h[i][1] -= c;
angle = M_PI/2 - atan (m);
rotate (h, angle);
for (i=0; i<9; i++)
h[i][0] = -h[i][0];
angle = -angle;
rotate (h, angle);
for (i=0; i<9; i++)
h[i][1] += c;
}

void ini()
{
int gd=DETECT,gm;
initgraph(&gd,&gm,"..\\bgi");
}
void dini()
{
getch();
closegraph();
}
void main()
{

int h[9][2],sx,sy,x,y,m,c,choice;
do
{
clrscr();
printf("1. Scaling about the origin.\n");
printf("2. Scaling about an arbitrary point.\n");
printf("3. Reflection about the line y = mx + c.\n");
printf("4. Exit\n");
printf("Enter the choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1: printf ("Enter the x- and y-scaling factors: ");
scanf ("%d%d", &sx, &sy);
ini();
reset (h);
draw (h);getch();
scale (h, sx, sy);
cleardevice();
draw (h);
dini();
break;

case 2: printf ("Enter the x- and y-scaling factors: ");
scanf ("%d%d", &sx, &sy);
printf ("Enter the x- and y-coordinates of the point: ");
scanf ("%d%d", &x, &y);
ini();
reset (h);
translate (h, x, y);// Go to arbitrary point
draw(h); getch();//Show its arbitrary position
cleardevice();
translate(h,-x,-y);//Take it back to origin
draw(h);
getch();
cleardevice();
scale (h, sx, sy);//Now Scale it
draw(h);
getch();
translate (h, x, y);//Back to Arbitrary point
cleardevice();
draw (h);
putpixel (320+x, 240-y, WHITE);
dini();
break;
case 3: printf ("Enter the values of m and c: ");
scanf ("%d%d", &m, &c);
ini();
reset (h);
draw (h); getch();
reflect (h, m, c);
cleardevice();
draw (h);
dini();
break;
case 4: exit(0);
}
}while(choice!=4);
}

OUTPUT



1. Scaling about the origin followed by translation.


2. Scaling with reference to an arbitrary point.



3. Reflect about the line y = mx + c.

INPUT

#include<stdio.h>
#include<graphics.h>
void main()
{
int gd=DETECT,gm;
initgraph(&gdriver,&gmode,"C//TurboC3//BGI");
int x1,y1,x2,y2 ;
float b1,b2;
float t,deg;
printf(“Enter the coordinates of Line: ”);
scanf(“%d%d%d%d”,&x1,&y1,&x2,&y2);
setcolor(6);
line(x1,y1,x2,y2);
getch();
//cleardevice();
printf(“Enter the angle of rotation: “);
scanf(“%f”,&deg);
t=(22*deg)/(180*7);
b1=abs((x2*cos(t))-(y2*sin(t)));
b2=abs((x2*sin(t))+(y2*cos(t)));
line(x1,y1,b1,b2);
getch();
closegraph();
}

OUTPUT

INPUT

#include<graphics.h>
#include<conio.h>
#include<stdlib.h>

main()
{
int gd = DETECT, gm, area, temp1, temp2, left = 25, top = 75;
void *p;

initgraph(&gd,&gm,"C:\\TC\\BGI");

setcolor(YELLOW);
circle(50,100,25);
setfillstyle(SOLID_FILL,YELLOW);
floodfill(50,100,YELLOW);

setcolor(BLACK);
setfillstyle(SOLID_FILL,BLACK);
fillellipse(44,85,2,6);
fillellipse(56,85,2,6);

ellipse(50,100,205,335,20,9);
ellipse(50,100,205,335,20,10);
ellipse(50,100,205,335,20,11);

area = imagesize(left, top, left + 50, top + 50);
p = malloc(area);

setcolor(WHITE);
settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2);
outtextxy(155,451,"Smiling Face Animation");

setcolor(BLUE);
rectangle(0,0,639,449);

while(!kbhit())
{
temp1 = 1 + random ( 588 );
temp2 = 1 + random ( 380 );

getimage(left, top, left + 50, top + 50, p);
putimage(left, top, p, XOR_PUT);
putimage(temp1 , temp2, p, XOR_PUT);
delay(100);
left = temp1;
top = temp2;
}
getch();
closegraph();
return 0;
}

OUTPUT

INPUT

#include<graphics.h>
#include<conio.h>
int main(){
int gd = DETECT,gm;
initgraph(&gd, &gm, "C:\\TURBOC3\\BGI");
setcolor(WHITE);
rectangle(150,180,250,300);
rectangle(250,180,420,300);
rectangle(180,250,220,300);
line(200,100,150,180);
line(200,100,250,180);
line(200,100,370,100);
line(370,100,420,180);
setfillstyle(SOLID_FILL, BROWN);
floodfill(152, 182, WHITE);
floodfill(252, 182, WHITE);
setfillstyle(SLASH_FILL, BLUE);
floodfill(182, 252, WHITE);
setfillstyle(HATCH_FILL, GREEN);
floodfill(200, 105, WHITE);
floodfill(210, 105, WHITE);
getch();
closegraph();
return 0;
}

OUTPUT

#include<stdio.h>
#include<conio.h>
#include<graphics.h>
void floodFill(int, int, int, int);
int midx=319, midy=239;
void main()
{
int gdriver=DETECT, gmode, x,y,r;
initgraph(&gdriver, &gmode, "C:\\TURBOCS3\\BGI");
cleardevice();
printf("Enter the Center of circle (X,Y) : ");
scanf("%d %d",&x,&y);
printf("Enter the Radius of circle R : ");
scanf("%d",&r);
circle(midx+x,midy-y,r);
getch();
floodFill(midx+x,midy-y,13,0);
getch();
closegraph();
}

void floodFill(int x, int y, int fill, int old)
{
if(getpixel(x,y) == old)
{
putpixel(x,y,fill);
delay(5);
floodFill(x+1,y,fill,old);
floodFill(x-1,y,fill,old);
floodFill(x,y+1,fill,old);
floodFill(x,y-1,fill,old);
}
}

OUTPUT

INPUT

#include<stdio.h>
#include<graphics.h>
#include<math.h>
#include<dos.h>
void main()
{
int i,gd=DETECT,gm;
int x1,y1,x2,y2,xmin,xmax,ymin,ymax,xx1,xx2,yy1,yy2,dx,dy;
float t1,t2,p[4],q[4],temp;
x1=120;
y1=120;
x2=300;
y2=300;
xmin=100;
ymin=100;
xmax=250;
ymax=250;
initgraph(&gd,&gm,"c:\\turboc3\\bgi");
rectangle(xmin,ymin,xmax,ymax);
dx=x2-x1;
dy=y2-y1;
p[0]=-dx;
p[1]=dx;
p[2]=-dy;
p[3]=dy;
q[0]=x1-xmin;
q[1]=xmax-x1;
q[2]=y1-ymin;
q[3]=ymax-y1;
for(i=0;i<4;i++)
{
if(p[i]==0)
{
printf("line is parallel to one of the clipping boundary");
if(q[i]>=0)
{
if(i<2)
{
if(y1<ymin)
{
y1=ymin;
}
if(y2>ymax)
{
y2=ymax;
}

line(x1,y1,x2,y2);
}
if(i>1)
{
if(x1<xmin)
{
x1=xmin;
}

if(x2>xmax)
{
x2=xmax;
}
line(x1,y1,x2,y2);
} } } }
t1=0;
t2=1;
for(i=0;i<4;i++)
{
temp=q[i]/p[i];
if(p[i]<0)
{
if(t1<=temp)
t1=temp;
}
else
{
if(t2>temp)
t2=temp;
}
}
if(t1<t2)
{
xx1 = x1 + t1 * p[1];
xx2 = x1 + t2 * p[1];
yy1 = y1 + t1 * p[3];
yy2 = y1 + t2 * p[3];
line(xx1,yy1,xx2,yy2);
}
delay(50000);
closegraph();
getch();
}

OUTPUT

INPUT

#include<stdio.h>
#include<graphics.h>
#define ScreenWidth getmaxx()
#define ScreenHeight getmaxy()
#define GroundY ScreenHeight*0.75
int ldaisp=0;
void DrawManWithUmbrella(int a,int ldaisp)
{
//Draw Umbrella
pieslice(a+20,GroundY-120,0,180,40);
line(a+20,GroundY-120,a+20,GroundY-70);
//Draw head
circle(a,GroundY-90,10);
line(a,GroundY-80,a,GroundY-30);
//Draw hand
line(a,GroundY-70,a+10,GroundY-60);
line(a,GroundY-65,a+10,GroundY-55);
line(a+10,GroundY-60,a+20,GroundY-70);
line(a+10,GroundY-55,a+20,GroundY-70);
//Draw legs
line(a,GroundY-30,a+ldaisp,GroundY);
line(a,GroundY-30,a-ldaisp,GroundY);
}
void Rain(int a)
{
int i,rx,ry;
for(i=0;i<400;i++)
{
rx=rand() % ScreenWidth;
ry=rand() % ScreenHeight;
if(ry<GroundY-4)
{
if(ry<GroundY-120 || (ry>GroundY-120 && (rx<a-20 || rx>a+60)))
line(rx,ry,rx+0.5,ry+4);
}
}
}
void main()
{
int gd=DETECT,gm,a=0;
initgraph(&gd,&gm,"C:\\TC\\BGI");

while(!kbhit())
{
//Draw Ground
line(0,GroundY,ScreenWidth,GroundY);
Rain(a);
ldaisp=(ldaisp+2)%20;
DrawManWithUmbrella(a,ldaisp);
delay(40);
cleardevice();
a=(a+2)%ScreenWidth;
}
getch();
}

OUTPUT

INPUT

#include<graphics.h>
#include<conio.h>
main()
{
   int gd = DETECT,gm,left=100,top=100,right=200,bottom=200,x= 300,y=150,radius=50;

   initgraph(&gd, &gm, "C:\\TC\\BGI");

   rectangle(left, top, right, bottom);
   circle(x, y, radius);
   bar(left + 300, top, right + 300, bottom);
   line(left - 10, top + 150, left + 410, top + 150);
   ellipse(x, y + 200, 0, 360, 100, 50);
   outtextxy(left + 100, top + 325, "My first C graphics program");

   getch();
   closegraph();
   return 0;
}

OUTPUT

IINPUT

#include<stdlib.h>
#include<conio.h>
#include<dos.h>
#include<graphics.h>
#include<ctype.h>

void main()
{
        int gd=DETECT,gm;
        int xincr=0,newy=0,yincr=5;

        initgraph(&gd,&gm," ");
        cleardevice();
        while(!kbhit())
        {
                ellipse(520-xincr,200,30,330,90,30);
                circle(450-xincr,193,3);
                line(430-xincr,200,450-xincr,200);
                line(597-xincr,185,630-xincr,170);
                line(597-xincr,215,630-xincr,227);
                line(630-xincr,170,630-xincr,227);
                line(597-xincr,200,630-xincr,200);
                line(597-xincr,192,630-xincr,187);
                line(597-xincr,207,630-xincr,213);
                line(500-xincr,190,540-xincr,150+newy);
                line(530-xincr,190,540-xincr,150+newy);
                if(xincr>=500)
                        xincr=0;
                if(newy>=82)
                        yincr=-5;
                xincr=xincr+5;
                if(newy<=0)
                        yincr=5;
                newy=newy+yincr;
                delay(50);
                cleardevice();
        }
        cleardevice();
}

OUTPUT