Course Information Instructor: Abdülkadir Görür
Office L210 Phone 2331340 Email: [email protected]
Instructor: Murat Saran
Office L209 Phone 2331333 Email: [email protected]
Instructor: Sibel Tarıyan Ozyer
Office L204 Phone 2331347 Email: [email protected]
Course is about: Introduction to C programming language
Topics
• The structure of a C program
• Variables
– Variable declaration
– Initialization
– Assignment
• Basic Input/Output operations
– printf
– scanf
The Structure of a C Program
#include<stdio.h> Declare which instructions will be used
void main() program always starts from main
{
/* variable declaration */
int i; Variables should be declared at the
beginning of the program
/* program statements */
printf(" A very simple C program \n");
}
Comments
Comments are used to explain the instructions
Comments are not executed
Any expression after // is considered as comment
Any expression between /* and */ is considered as
comment
Comments
Example
void main()
{
// this line is a comment
int t = 10;
/* this is another comment */
printf(“%d\n”, t);
}
Main Features of a C Program
A C program should have a main() part. The program
starts with this part.
The instructions of a C program are written inside the
body of main() which is shown with { and }
Each instruction ends with a ; character
The Structure of a C Program
#include<stdio.h> Declare which instructions will be used
void main() program always starts from main
{
/* variable declaration */
int i; Variables should be declared at the
beginning of the program
/* program statements */
printf(" A very simple C program \n");
}
Variables
The input or output data should be stored in memory
Memory locations for storing values temporarily are called
variables.
Variables are accessed by their names
The type of the data stored in a variable should be given
Declaring Variables
All variables should be declared before use
For declaration
Variable _Type Variable_Name;
Variable types: int (or long), float (or double),
char Ex. int i;
float account;
Declaring Variables
Variable name should start with a letter
Variable name cannot be a key word (like if, else, switch,
for, while, … )
No blank character is allowed in a name
_ (underscore) can be used in the variable names Ex.
New_box
A combination of letters and digits can be used as variable
names. e.g. Num2
Upper and lower case characters are different
Ex. Name and name are different
Initialization
Variables can be given initial values at declaration
Ex. float average=0;
char letter=‘A’;
Assignment
• “Assignment” gives values to variables
• Assignment is done by = operator
• At the left side of = symbol, we must have a variable name Ex. int speed_limit;
speed_limit = 50; Values are converted if they are not of the type of the variable
Ex. float delay; delay = 12; /* is converted to 12.0 */
int max;
max = 16.2; /* truncated to 16 */
Assignment
In character variables, the ASCII code of the character is
stored.
Ex.
int a;
char c;
c=‘A’;
a=c; /* at a we will have 65 (the ASCII code of ‘A’ ) */
Assignment
Multiple assignments are allowed in C
Ex.
int a,b,c;
a=b=c=5;
5 is stored in all variables
Basic Input / Output
Input instructions are used to get a value from the user and
store it in a variable
Output instructions are used to write a value to some output
device such as Monitor
Output Command: printf
printf( format string, variables );
Format string defines the variable types
%d decimal (int)
%f float
%c char
\n new line
Format string is written using “” marks
e.g. “%d\n” print an integer and then go to a new line
Examples
int a = 15;
float k=4.5;
char m=‘L’ ;
printf(“%d %f %c \n”,a,k,m);
printf(“First number is = %d\n”,a);
printf(“%5.2f”,k);
/* uses 5 digits totally including ‘.’ having 2 of them after ‘.’ */
Input Command: scanf
scanf( format string, &var1, &var2,..);
scanf has the same format as printf
Put an & character before the name of the variables
Example Read three integer, float and character values and print them #include<stdio.h>
void main() { /* variable declaration */ int i;
float R; char t_type; scanf("%d%f%c",&i,&R,&t_type); printf(" The values entered are %d and %f and %c \n“,i,R,t_type);
}
Escape Sequences
Escape sequences are used to define output format.
For example, to start a new line, or to print special
characters we use Escape sequences
Example
Write a C program to read 2 characters, an integer and a
floating point number . Then print them
#include <stdio.h>
void main() {
char c1,c2;
int num; float fnum;
scanf(“%c%c”,&c1, &c2);
scanf(“%d%f”,&num,&fnum);
printf(“The characters are : %c and %c \n”, c1,c2); printf(“The numbers are : %d and %f\n”, num, fnum); }
Summary
A C program contains a main() part which includes the
instructions
Variables are used to store values
Assignment operator (=) is used to give value to a variable
scanf and printf are used to read values and to write values
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