CHAPTER-4
C PROGRAMMING FOR
PROBLEM-SOLVING
Sayooj Devadas K
C was developed at Bell Labs by
Dennis Ritchie between the years
1972 and 1973. C is one of the
oldest general purpose
programming languages of all time
and it was developed to construct
utilities running on Unix and was
applied to re-implement the kernel
of the Unix operating system.
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Advantages of C Language :
•Simple: easy to learn , offer structural approach to solve
problems
•Portable: C programs can be written on one platform and
can be executed in the same way on another operating
system. C is a machine-independent language.
•Structured programming language: C provides different
functions that enable us to break the code into small parts,
that is why C programs are easy to understand and modify.
Functions also offer
code reusability.
•Fast and Efficient: The compilation and execution time of
the C language is also fast.
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C
Python
Low-level language, closer to machine
language
High-level language, further from machine
language
Statically-typed, requires explicit variable
declaration
Dynamically-typed, variables do not need
to be declared beforehand
Prioritizes performance and control
Prioritizes readability and ease of use
Used for system programming, embedded
systems, and performance-critical applications
Used for general-purpose programming,
scripting, and data analysis
Procedural Oriented programming language
Object Oriented programming language
Uses compiler
Uses Interpreter
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C BASIC COMMANDS:
#include <stdio.h>
It is a preprocessor command which consists of a standard
input output header file(stdio.h) before compiling a C
program.
int main()
The main function from where execution of any C program
starts.
{
Indicates the beginning of the main function.
}
The function or method block is closed with these curly braces.
/*_some_comments_*/
Any content inside “/* */” will not be used for compilation and
execution.
printf
The output is printed to the console screen using this C
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return
This C function returns 0 after terminating the C programme or
main function.
Scanf
The user data is taken from the usual console terminal window
using this C function. (similar to input() in python)
//
Used for ingle line comments,
/*_some_comments_*/
Any content inside “/* */” will not be used for compilation and
execution.
printf
The output is printed to the console screen using this C
return
This C function returns 0 after terminating the C programme or
main function.
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HEADER
FILES IN C
• Header files are external libraries.
- By adding header files to your code,
you get additional functionality that you
can use in your programs without
having to write the code from scratch.
• #include is a preprocessor command
that tells the C compiler to include a
file.
• The stdio.h header file stands for
standard input-output. It contains
function definitions for input and
output operations
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SIMPLE C PROGRAM(HELLO
WORLD PROGRAM)
#include <stdio.h>
int main (void)
{
printf("\n Hello World \n");
return 0;
}
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WHAT IS THE MAIN()
FUNCTION IN C
•
“ int main(void) { …} ’’ is the main function and starting
point of every C program.
•
It is the first thing that is called when the program is
executed.
The int keyword in “int main(void) { .. }” indicates the
return value of the main() function.
Anything inside the curly braces, {}, is considered the
body of the function
•
•
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We need to save the file with a
`.c` extension, or it won’t be a
valid C file.
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WHAT IS SEMICOLON ‘;’ IN C
• The semicolon, ;, terminates the statement.
• All statements need to end with a semicolon
in C, as it identifies the end of the statement.
• You can think of a semicolon similar to how a
full stop/period ends a sentence.
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EXAMPLE OF SYNTAX ERROR IN C
#include <stdio.h>
void main() {
var = 5; // we did not declare the data type of
variable
printf("The variable is: %d", var);
}
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output:
error: 'var' undeclared (first use in this function)
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DATA TYPES IN C
• Data types used in C language declare
various types of functions or variables
in a program.
• Based on the type of variable present
in a program, we determine the space
that it occupies in storage
• A data type specifies the type of data
that a variable can store such as
integer, floating, character, etc.
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Relational Operators
•Relational operators are binary operators
that evaluate the truthhood or falsehood
of a relationship between two arguments
and produce a value of true ( 1 ) or false (
0 ) as a result.
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Logical Operators
• Logical operators are used to combine
and evaluate boolean expressions,
generally in combination with the
relational operators we discussed in
previously.
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Example: To determine whether x is between
5.0 and 10.0:
• INCORRECT: 5.0 < x < 10.0
• CORRECT: 5.0 < x && x < 10.0
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Example: Finding Leap year
Leap year occurs when the current year is divisible by 4, but NOT when the
year is divisible by 100, UNLESS the year is also divisible by 400
int year;
bool leap_year;
leap_year = ( ( ( ( year % 4 ) == 0 ) && ( ( year % 100 ) !=
0 ) ) || ( ( year % 400 ) == 0 ) );
// Or equivalently:
leap_year = !( year % 4 ) && year % 100 || !( year % 400 );
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printf() function
printf ( "formatted_string", arguments_list);
#include <stdio.h>
int main()
{
printf("Hello world!");
return 0;
}
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Specifier
It is the character that denotes the type of data.
Some commonly used specifiers are:
•%d: for printing integers
•%f: for printing floating-point numbers
•%c: for printing characters
•%s: for printing strings
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#include <stdio.h>
int main()
{
int num1 = 99;
int num2 = 1;
printf("The sum of %d and %d is %d\n", num1, num2,
num1 + num2);
return 0;
}
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if-else
•"if" blocks and "if-else" blocks are used to make
decisions, and to optionally execute certain code.
•The general syntax of the if-else structure is as
follows:
if( condition )
true_block
else
false_block
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• Example:
if( x < 0.0 ) {
printf( "Error - The x coordinate
cannot be negative. ( x = %f ) \n", x );
exit( -1 );
}
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FOR LOOP
for (initializationStatement; testExpression; updateStatement)
{
// statements inside the body of loop
}
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• The initialization statement is executed only
once.
• Then, the test expression is evaluated. If the
test expression is evaluated to false, the for loop
is terminated.
• However, if the test expression is evaluated to
true, statements inside the body of the for loop
are executed, and the update expression is
updated.
• Again the test expression is evaluated.
• This process goes on until the test expression
is false. When the test expression is false, the
loop terminates.
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COMPARISON BETWEEN PYTHON
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BREAK IN C
• break statement is used to exit a loop
(for, while or do-while loop) or
a switch statement immediately, without
waiting for the loop or switch to finish its
normal execution cycle.
• Syntax :
• break;
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CONTINUE IN C
• Continue statement in C is used within
looping constructs (for, while & do-while
loops). When the continue statement is
encountered, the current iteration of the
loop is terminated immediately, and the
loop’s controlling expression is reevaluated to determine if the loop should
continue with the next iteration.
• Syntax :
• continue;
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EXAMPLE: PROGRAM THAT PRINTS
EVEN NUMBERS BETWEEN 1 AND
50.
#include <stdio.h>
int main() {
int i;
printf("Printing even numbers between 1 and 50:\n");
for (i = 1; i <= 50; i++) {
if (i % 2 != 0) {
continue; // Skip odd numbers
}
printf("%d\n", i);
}
return 0;
}
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USER-DEFINED FUNCTIONS
Syntax :
returnType functionName (parameter1, parameter2,...)
{
// function body
}
// function declaration
void hello()
{
printf("Hello World!");
}
In the above example,
•the name of the function is hello()
•the return type of the function is void
•the empty parentheses mean it doesn't
have any parameters
•the function body is written inside {}
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int main() {
// calling a function
hello();
}
Calling a function
• When a program calls a function, program control is
transferred to the called function.
• A called function performs defined task and when
it's return statement is executed, it returns program
control back to main program.
• To call a function, we need to pass the
requirement parameters along with function name, and
if function returns a value, then we can store returned
value.
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Function Parameters
void printnum(int a) {
printf("%d ", a);
}
int main() {
int a = 7;
// calling the function
// a is passed to the function as argument
printnum(a);
return 0;
}
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#include <stdio.h>
int add(int a, int b) {
return (a + b);
}
int main() {
int sum;
// calling the function and storing
// the returned value in sum
sum = add(10, 50);
printf("10 + 50 = %d", sum);
return 0;
}
Output:
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ARRAY
An array is a variable which is used to store a
collection of similar type of data items
stored at contiguous memory locations. This
is similar to the concept of lists in Python.
Syntax:
Datatype Array_name[Array_size] = { element1, ...........};
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Example :
int num[10] = {1,2,3,4,5,6,7,8,9,0};
int marks[] = {11,12,13,14,15,16,17,18,19,20};
In the above example, we have declared an integer type
array num[10] having size of 10 i.e. it can store maximum 10
integer values.
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//Program to print an element of an array
#include <stdio.h>
void main() {
int num[5] = {3,2,4,6,7};
printf("%d ", num[3]);
}
Output :
6
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Question
//Program to change value of element of an array
#include <stdio.h>
void main() {
int num[5] = {1, 2, 3, 4, 5};
num[3] = 10;
num[0] = 9;
for(int b = 0; b < 5; b++) {
printf("%d ", num[b]);
}
}
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OUTPUT:
9 2 3 10 5
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SCANF() - TAKE INPUT
scanf() function is used to take input of the
user read numeric data, character from
keyboard.
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Example : Take Integer Input
#include <stdio.h>
int main(){
int num;
printf("Enter a number: ");
scanf("%d", &num);
printf("Your entered number is %d",num);
return 0;
}
Output
Enter a number : 12
Your entered number is 12
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Input and Output Array Elements
#include <stdio.h>
int main() {
int a, b, num[5];
printf("Enter a integer : ");
for(a = 0; a < 5; a++) {
scanf("%d", &num[a]);
}
printf("Elements in the array : ");
for(b = 0; b < 5; b++) {
printf("%d ", num[b]);
}
return 0;
} 20XX
Output :
Enter a integer : 2
5
6
1
9
Elements in the array : 2
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MULTI-DIMENSIONAL
ARRAYS
•The data in multi-dimensional array is stored in a tabular form
(row * column) as shown in the diagram below.
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Initialization of two-dimensional array
Syntax:
Data_type array_name[x][y];
First method :
int arr[2][3] = {2, 0, 3, 5, 1, 12};
Better method :
int arr[2][3] = { {2, 0, 3}, {5, 1, 12}};
Here we initialize a 2D array arr, with 2 rows and 3 columns as an array of arrays.
Total elements in this array : 2 * 3 = 6 , and Each element of the array is yet again
an array of integers.
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Example : Taking Input from user for Two Dimensional Array
#include <stdio.h>
int main(){
int a[2][2], i, j;
// Taking input using nested for loop
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
printf("Enter a[%d][%d] : ", i, j);
scanf("%d", &a[i][j]);
}
}
printf("\n All the elements of matrix : \n");
// Printing Output using nested for loop
for (i = 0; i < 2; ++i) {
for (j = 0; j < 2; ++j) {
printf("a[%d][%d] : %d\n", i, j, a[i][j]);
}
}
return 0;
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• In the previous program, we have used a
nested for loop to take the input of the
2D array.
• Once all the input has been taken, we
have used another nested for loop to print
the array members.
• Finally, we print the array elements in each
iteration.
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