1. F1001 PROGRAMMING FUNDAMENTALS
UNIT
5
STRUCTURE OF C PROGRAM
 Basic Concepts of C Programming
 Important Elements In A C Program
 Data and Variables
 Input and Output
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2. F1001 PROGRAMMING FUNDAMENTALS
INTRODUCTION
In this unit students are introduced to a simple C program. The unit describes the important elements of a
C program and the types of data that can be processed by C. It also describes C statements for performing
tasks such as getting data from the user and displaying the data on screen. Here students will be presented
with examples that illustrate many important features of C programming.
At the end of this unit, students should be able to write simple C programs in accordance to the rules and
conditions of C programming. By this time, they should know the ways to declare variables, use variables
and understand the naming conventions of variables and print outputs. Students should also have enough
knowledge to write clear, well documented and error free codes at the end of this chapter.
Basic C program structure
Comments
/* Example of basic C program Structure */
#include <stdio.h> Header File
Pre-processor
commands #define MAX 20
void main() Main Function
{ Start of main function
Constant const PI = 3.142;
Data Type char letter;
Variable
int number;
huruf = ‘A’;
Output Function printf(“Enter one number : “);
Input Function scanf(“%d”, &number);
} End of main function
NOTES
The curly braces “{ }” symbol shows the body of the program body. Any code/statements must
be written inside the body.
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3. F1001 PROGRAMMING FUNDAMENTALS
Comments
• A line starting with /* and ending with */ is a comment.
• The purpose of a comment is to document and understand the program. It can be used to tell what is the
purpose of using variables or functions. It also enables your program to be easily understood by others.
• Comment will not be executed by the compiler.
• A good programming practice is to have comments in the program
Examples :
/* this is a comment */
/* This is
also
a comment */
Main function and functions
• Every C program contains a main function which is called main()
• Program execution starts from this main function.
• main() function has two parts:
main() (i) head
{
char b;
b = ‘A’; (ii) body
}
HEAD BODY
• Every function must have a header. • Every function must have a body which starts
• Function header is the name of that function. with an open curly bracket ‘{’ and ends with
• main() function has a fixed name. a close curly bracket ‘}’.
• We cannot change the name of main() • Every body function contains a program
function statement.
• A program statement will perform certain
tasks such as receiving value, display value,
calculation and so on.
Pre-processor Commands
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4. F1001 PROGRAMMING FUNDAMENTALS
• #include <stdio.h>
# • Lines starting with the ‘#’ symbol is processed by the pre-processor,
before compiling the program.
#include • Is known as pre-processor directive.
• Each pre-processor directive has its own header file.
• Pre-processor directive gives instruction so that manipulation can be
done on the programs. Example, by instructing the processor to
include other files that are needed by the program.
#include
<FileName>
or
<stdio.h> • Used for the process of displaying output on the screen or getting
input from the user via the keyboard ( example printf and scanf)
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5. F1001 PROGRAMMING FUNDAMENTALS
• #define AGE 22
# • Lines starting with the ‘#’ symbol is processed by the pre-processor,
before compiling the program.
#define • It does a search-and-replace command on a word processor
(editor)
#define <constant name> <constant value>
AGE • Name of constant
• Usually written in CAPITAL letters
22 • Value assigned to AGE
Examples of Header Files in C programming
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6. F1001 PROGRAMMING FUNDAMENTALS
HEADER LIBRARY USES
FILES FUNCTIONS
stdio.h scanf()  Receives input from keyboard
printf()  Displays output on screen
gets()  Receives input in the form of string
getchar()  Receives a character as input
puts()  Displays output in string form
math.h pow(x,y)  Computes the value of x raised to the power of y
sqrt(x)  Computes the square root of x
exp(x)  Computes the exponent value of x
ctype.h isalnum(c)  To test whether c is alphabetic or digit
isdigit(c)  To test whether c is a numeric
ispunct(c)  To test whether c is a punctuation mark
islower(c)  To test whether c is a lower case character
string.h strlen(c)  To get the length of a string
strncmp(c)  Compares the part of two strings
strtok(c)  Splits string into words
strncpy(c)  Copies one part of a chosen string
conio.h clrscr()  Clears the output screen
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7. F1001 PROGRAMMING FUNDAMENTALS
Data and Variables
Data
 Data is an array of facts that can be modified by the computer into useful forms for human beings.
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8. F1001 PROGRAMMING FUNDAMENTALS
NUMERIC INTEGER
 All positive and negative numbers including zero and
• Contains all types of no decimal place.
numbers.  Example: 0, +1, -10.
• Data which can be used  Integers are used to represent the counting of things.
for calculation. Example: Numbers of month in a year (1,2,3…)
• Example: sums of
REAL NUMBER
money, age, and
 Contains all real numbers.
distance (e.g: 34, 50,
 The number will be stored in floating point.
and 1.01).
 Used for metric measurement, temperature and price.
Example: 1.0, 234.55, 20.30, 36.7.
CHARACTER
 Consists of all letters, numbers and special symbols.
 Characters are surrounded by single quotation mark (‘
‘).
DATA
Example: ‘A’, ‘m’,’=’, ‘#’, ‘1’ or ‘ ‘.
STRING
 A combination of one or more characters.
NON NUMERIC  A string is surrounded by double quotation marks (“
“).
Example: (“WELCOME TO COSMOPOINT”) or
(“8758”).
LOGICAL VALUES
• Used in making yes-or-no decisions (TRUE-or-
FALSE).
Example: To check 2 integers using If…Else control
structure.
Variables
• A variable is a place to store a piece of information. Just as you might store a friend’s phone
number in your own memory.
• Each variable has:
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9. F1001 PROGRAMMING FUNDAMENTALS
1. Name
2. Type
3. Holds a value that you assign to them
• Must begin with a letter of the alphabet but, after the first letter,
Naming Variables
it can contain:
1. Letters: A……Z, a……..z
2. Number : 0……9
3. Underscore character: _
• Variable names are case-sensitive (example: the variable
"mYNUMBER" is different from the variable "MYNUMBER").
• Cannot be more than 31 characters.
• Variable names cannot be the same as the C reserved words.
• Variable names cannot have spaces.
Examples : my age count 1 student 10
• Variable names cannot have special characters (typographic
symbols).
Examples : ? / ~ @ + $
Valid Variables Names • Examples : MyAge123, myAGE, My_Age, my_age, NAME,
Name.
• Examples: MY AGE, 4_stu, my age, printf, 81_sales,
Invalid Variable Names Aug91+Sales, Age?
Defining Variables Syntaks : DataType VariableName;
Examples : int number; float money;
Assigning Values To Syntaks : VariableName = Expression
Variables
Examples : number = 32; money = 30.50;
Data Types
• Data type is the type of data that will be stored in the memory location.
DATA TYPE USES EXAMPLE CODE
int int is used to define integer
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10. F1001 PROGRAMMING FUNDAMENTALS
numbers. int Count;
Count = 5;
float float is used to define floating point
numbers. float Miles;
Miles = 5.6;
double A double is used to define BIG
floating point numbers. It reserves double Atoms;
twice the storage for the number. Atoms= 2500000;
char A char defines characters.
char Letter;
Letter = 'x';
Variable Scope
 There are two main variable scopes:
1. Local variable
2. Global variable
Local Variable Global Variable
#include <stdio.h> #include <stdio.h>
FunctionName() char B;
{
int A; FunctionName()
{
/*Block of one or more */ / int A;
*C statements*/
} /*Block of one or more */
/*C statements*/
}
Local Variable
Global
Variable
 It is a variable that has been defined  A global variable is a variable that has been
immediately after the opening braces of a defined before a function (usually before the
function. main() function).
 Each functions can have their own variables  This means, all function in that program can
declarations. use this variable.
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11. F1001 PROGRAMMING FUNDAMENTALS
 You can access (and change) local variables  Global variables can be used anywhere in
only from the functions in which they are the program as soon as it has been defined.
defined. Therefore that variable's scope is
protected.
 All local variables lose their definition when
their block ends.
Character And String Array
• Array is a list of variables or constants, and most programming languages allow the use of such lists.
• A character array is the place to hold strings of information.
• A string is a collection of characters to represent a name
How to define
(mother, father, student, employee, car, building, shopping
strings data type
complex, software), address and extra.
Syntaks:
char variableName [STRING_LENGTH];
Example to declare
char employeeName [30];
character array:
 A string must be stored in character arrays, but not all
character arrays contain a string.
string
Contoh :
char name[9] = "Muhammad";
is not the same as
char name[8] = {'M', 'u', 'h', 'a', 'm', 'm', 'a', 'd'};
Data String
Variable Name
Type length
Character array
Constant
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12. F1001 PROGRAMMING FUNDAMENTALS
• The value of constant remains unchanged for the whole duration of the program execution.
• Every constant has :
1. Name
2. Type
3. Values that are set to them
Syntax : const data_type constant_name = constant_value;
or
#define constant_name constant_value
Examples :
const double PI = 3.1459;
#define PI 3.1459
Character Conversion
• This sign % is known as conversion character in C language.
• Conversion character is used to tell the input function (scanf()) and the output function (printf())
about how the data is being accepted or viewed.
• Examples of usage (input function):
int a; char b; char c[5]; float d;
scanf(“%d”, &a); scanf(“%c”, &b); scanf(“%s”, c); scanf(“%f”, &d);
• Examples of usage (output function) :
printf(“Integer %d”, a); printf(“Aksara Tunggal %c”, b);
printf(“Rentetan %s”, c); printf(“Titik apung %f”, d)
%d decimal integer
%s string
%c character
%e exponential notation floating point number
%f float
%g use the short if %f or %e
%u unsigned integer
%o octal integer
%x hexadecimal integer 81
%% percent sign (%)

13. F1001 PROGRAMMING FUNDAMENTALS
Input And Output
Input Function Output Function
• Use the scanf(), gets(), getc() and • Use the printf(), puts() and putchar()
getchar() function from the stdio.h. function from stdio.h
• One of way to get input is by asking the • This function sends all the output to the
user to enter values into the variables using screen.
the keyboard.
Syntax : printf(“CS”,variablename)
• It contains conversion characters.
• The conversion character explains to C
what data type to be inserted by user.
CS: Control String – a combination of string and
Syntax : scanf(“CC”, &variablename);
conversion character
CC – Conversion Character
#include <stdio.h>
#include <stdio.h> main ()
{
main() int age;
{ /*Input*/
char name [35]; printf(“Your age ?”);
scanf(“%d”, &age);
/*Input*/ /*Output*/
printf(“Enter name :”); printf(“Your age : %d years”, age);
scanf(“%s”, name); }
}
Control String
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