INTRODUCTION TO C-PROGRAMMING

CLanguage

Tutor

©  Ajani Dele

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Introduction

The C programming language was originally developed by Dennis Ritchie of Bell Laboratories, and was designed to run on a PDP-11 with a UNIX operating system. Although it was originally intended to run under UNIX, there was a great interest in running it on the IBM PC compatibles, and other systems. C is excellent for actually writing system level programs, and the entire Applix 1616/OS operating system is written in C (except for a few assembler routines).It is an excellent language for this environment because of the simplicity of expression, the compactness of the code, and the wide range of applicability.

C is a general-purpose programming language. It has been closely associated with the UNIX operating system where it was developed, since both the system and most of the programs that run on it are written in C. The language, however, is not tied to any one operating system or machine; and although it has been called a “system programming language” because it is useful for writing compilers and operating systems, it has been used equally well to write major programs in many different domains.

C provides the fundamental control-flow constructions required for well-structured programs: statement grouping, decision making (if-else), selecting one of a set of possible values (switch), looping with the termination test at the top (while, for) or at the bottom (do), and early loop exit (break).

Functions may return values of basic types, structures, unions, or pointers. Any function may be called recursively. Local variables are typically ``automatic'', or created anew with each invocation. Function definitions may not be nested but variables may be declared in a block-structured fashion. The functions of a C program may exist in separate source files that are compiled separately. Variables may be internal to a function, external but known only within a single source file, or visible to the entire program.

A preprocessing step performs macro substitution on program text, inclusion of other source files, and conditional compilation.

C is a relatively “low-level” language. This characterization is not pejorative; it simply means that C deals with the same sort of objects that most computers do, namely characters, numbers, and addresses. These may be combined and moved about with the arithmetic and logical operators implemented by real machines.

C provides no operations to deal directly with composite objects such as character strings, sets, lists or arrays. There are no operations that manipulate an entire array or string, although structures may be copied as a unit. The language does not define any storage allocation facility other than static definition and the stack discipline provided by the local variables of functions; there is no heap or garbage collection. Finally, C itself provides no input/output facilities; there are no READ or WRITE statements, and no built-in file access methods. All of these higher-level mechanisms must be provided by explicitly called functions. Most C implementations have included a reasonably standard collection of such functions.

Similarly, C offers only straightforward, single-thread control flow: tests, loops, grouping, and subprograms, but not multiprogramming, parallel operations, synchronization, or coroutines.

let's see some written programmes  

C program to sum the square of number using functions.

int sum;

/* this is a global variable*/

main( )

{

int index;

header();

/* this calls the function named header*/

for (index = 1;index <= 7;index++)

square(index); /* This calls the square function*/

ending();

/* This calls the ending function*/

}

header()

/* This is the function named header */

{

sum = 0;

/* initialize the variable "sum" */

printf("This is the header for the square program\n\n");

}

square(number)

/* This is the square function*/

int number;

{

int numsq;

numsq = number * number;

/* This produces the square*/

sum += numsq;

printf("The square of %d is %d\n",number,numsq);

}

ending()

/* This is the ending function*/

{

printf("\nThe sum of the squares is %d\n",sum);

}

C PROGRAM FOR QUADRATIC EQUATION

/* real roots of a quadratic equation*/

          #include <stdio.h>

          #include <math.h>

          Main()

{

float a, b, c, d, x1, x2;

/* read input data*/

Printf(“a=”);

Scanf(“%f”, &a);

Printf(“b=”);

Scanf(“%f”, &b);

Printf(“c=”);

Scanf(“%f”, &c);

/*carry out the calculation */

d=sqrt(b*b – 4*a*c);

printf(“a=%e b=%e c=%e d=%e\n”, a, b, c, d);

printf(“-b+d=%e\n”, (-b+d));

printf(“-b-d=%e\n”, (-b-d));

          x1 = (-b+d)/(2*a);

          x2 = (-b-d)/(2*a);

/*display the output*/

Printf(“\nx1 = %e x2 = %e”, x1, x2);

return 0;

}

C program which reads angle in radians and then prints equivalent angle in degree, minute and seconds.

#include<stdio.h>

#define pi 3.142

int main()

{

float r;

int d, m, s;

printf(“Enter angle in radian\n”);

scanf(“%f”, &r);

r=(r*180)/pi;

d=r;

r=(r-d)*60; /*calculating left over angle in minute*/

m=r;

s=(r-m)*60;

printf(“%d%d%d\n”, d, m, s);

return 0;

}

C program that read in angle in degree, minute, and seconds then print the equivalent in radian

#include <stdio.h>

int main()

{

int d, m, s;

float rad;

printf(“enter angle in degree, minutes, and seconds”);

/*reading angle in degrees, minutes, and seconds*/

Scanf(“%d%d%d”, &d, &m, &s);

rad = (d+(m/60.0)+(s/3600.0))*(3.14/180);

/*converting angle into radians*/

Printf(“%f\n”, rad);

return 0;

}

 C program to calculate the potential energy of a body

#include "stdafx.h"

#include "stdio.h"

#include "stdlib.h"

//#include "math.h"

int main ()

{

          float pe, m,h;

          char c;

          const float g = 9.8;

          printf("Enter the value for m and h"); /* reading in d value */

          scanf("%f", &m);

          scanf("%f", &h);

          pe = (m * g * h);  /* computation takes place here */

          /* display result */

          printf("mass=%f\n",m);

          printf ("height=%f\n", h);

          printf("PE=%-7.4f\n", pe);

           c = getchar();

           system ("pause");

#include "stdafx.h"

#include "stdio.h"

#include "stdlib.h"

int main ()

{

printf("C programming Give Birth to Object oriented language");

   getchar();

   system("pause");

          return 0;

}

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