Transcript Getting Started With Coding

Chapter 3
By:
Mr. Baha Hanene
Learning Outcomes
We will cover the learning outcome 02 in this chapter
i.e.
 Use basic data-types and input / output in C programs.
(L02)
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Contents
 Introduction to Programming
 Stages & Steps of Writing Programs
 Preprocessor Directives
 Main Function
 Output Statement
 Variables in C
 Assignment Statements
 Sample Programs
 References
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Programming Introduction
 A language which is used to instruct computer to
perform different tasks according to the requirements.
 Every programming language has following basic
things.
 Declarations
 Assignments
 Control
 I/O
Statements
(Input/output)
Statements
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Programming Introduction
 Any programming language consists of its own
keywords and syntax rules that distinguishes it from
other programming languages.
 If you want to program in a specific language, you
need the compiler of this specific language.
 For example, C language compiler translates programs
written in C language to machine language.
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Programming Style
 Keep it clear & simple
 Keep it short
 Think it through in advance
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Stages & Steps of Writing Programs
Specification
Design
Coding
Testing
Documentation
Maintenance
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Preprocessor Directives
 In C programming whenever you see lines that begin
with a
in column 1 are called preprocessor
directives (commands)
 The #include<stdio.h> directive allows the processor
to include basic Input / Output in the program at this
point.
#
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stdio.h
 This header file we include in all programs where we
need to use basic I/O commands e.g.
 printf(“”);
scanf(“”);
 Some functions are very difficult and very long to
write, these header files contains built in functions to
provide us help in writing the programs.
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void main( )
 Every C program has a main function, this is where the
program starts it’s execution, as this is the first
function to execute in the whole c program.
 The reserved word “void” shows that this function will
not return any value.
 Each C program can contain only one main function
e.g.
void main()
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Function Body
 A left brace (curly bracket) -- { -- begins the body of
BOD
Y
every function. A corresponding right brace -- } -ends the function body.
void main()
Main Function
{
……
……
}
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printf(“”);
 This line is called a C statement
 printf(“”); is a function which is used to instruct computer to
display something on computer screen
 All text, special symbols you will type inside printf(“”); between
the double quotations i.e. “……..” will be displayed as it is on your
computer screens except few commands like /t, /n, %i etc. e.g.
 printf(“Welcome at KIC”);
 Notice that the above line ends with a Semicolon
statement ends with a semicolon i.e. ;)
;
(every C
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Sample #include<stdio.h>
Program Explanation
Header File used for Input / Output
void main()
Function Start
Main Function Necessary
to start any C program
{
Output Statement
used to display on printf(“Hello to programming”);\n Start New Line
screen
printf(“\n Welcome at KIC”); \t
Give Space between text
printf(“\t at Fall 2010/11”);
Function End
}
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Variables in C
 In computer programming, a variable is a name given to
some known or unknown quantity or value, for the purpose
of allowing the name to be used independently of the value
it represents
 [Data Type][Variable Name] ;
Data Types: In C programming there are more data types
but we generally use the following data types. (more details in
next chapter)
1. int2. float
3. char
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Variables in C
 Variable Name: You can give any name to the variables in c
but there are few rules for writing variable names.
 (A-Z) The first character must be a letter
 Space is not allowed between names of identifiers
 (&*^%$#@) Special symbols are not allowed in identifier
names
 - Hyphens are not allowed in identifier names however
underscores _ can be used
 (int, float, private etc.) The reserve words are not allowed in
identifier names.
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Variables in C
Some valid identifiers / variable names
hello j9 box22a get_data bin3d4
count
 Some reserve words (can’t be used as identifier):
private else static int const float
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Variables
in C
velocity
freda
time-of-day
int
tax_rate
x2
4x
first value
radio@4
emp.
velocity
freda
time_of_day
INVALID
tax_rate
x2
x4
first_value
radio4
emp
RIGHT
RIGHT
RIGHT
RIGHT
RIGHT
WRONG
WRONG
WRONG
WRONG
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Variables in C
 How & where we write variables in C programming….?
 We usually declare all variables inside main function
for example:
#include<stdio.h>
Data Type
void main()
{
int avar ;
int salary ;
float percentage ;
}
Variable
Name
Semi Colon (every C
statement ends with a
semicolon ;)
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Sample Program
Multiple Variable Declaration
Any
Questions
?
???
?????
Assignment
Statements
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Assignment Statements
 Before using variables in assignment statements you should
define / declare them first e.g. int a;
 Assignment Statements
 first_number = 35;
 second_number = 21;
 sum = first_number + second_number;
 The first two statements assigns the values 35 and 21 to the
variables first_number and second_number respecitively
 The next statement assigns the sum of the two values to the
variable sum.
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Sample Program
Header File
Main Function
Variable Declaration
Function
Body
Assignment Statements
Screen Output
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Displaying
Variable
Value
 Do you see something different in normal printf
statements and these which we have seen in the last
sample program???
%d These are called Format
Specifiers used to display the
value stored in the variable i.e.
Inside computer memory
What are
these
things????
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Sample Program Output
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The Logical
Flow
Source Program
Compile
Syntax Error
OK
Object Code/ Program
Run
Run-time Error
OK
Result
Logical Error
OK
Continue
END
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References
 http://en.wikipedia.org
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