C programming day#1

With/Mohamed Fawzy
Quick Review for C basics
1 Day #1

2
Lecture Notes:
 Set your phone to vibration mode.
 Ask any time.
 During labs feel free to check any materials or internet.

3
Contents
 History of C programming language.
 Introduction to C programming language.
 Variables and data types.
 Expressions and operators.
 Decision making.
 Hands ON.

4
Contents
4
 History of C programming language.
 Introduction to C programming language.
 Variables and data types.
 Expressions and operators.
 Decision making.
 Hands ON.

C Programming History:
 In 1969, Dennis Ritchie and Ken Thompson at “AT&T”
labs (Bell Labs).
 C came into being in the years 1969-1973, in parallel
with the early development of the Unix operating
system.
 To make UNIX operating system portable.
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Why C in Embedded Systems?
6
Next program structure.
 C is very close to assembly programming and it allows very easy access
to underlying hardware. A huge number of high quality compilers and
debugging tools are available for the C language.
 Though C++ is theoretically more efficient than C, but some of its
compilers have bugs due to the huge size of the language. These
compilers may cause a buggy execution.
 C language can definitely claim to have more mature compilers C++. Now
in order to avail the extra benefits of C++ and plus to avoid buggy
execution, experts are doing efforts to identify a subset of C++ that can be
used in embedded systems and this subset is called Embedded C++

8
C program Structure.
/**information about the file*/
/**includes files and libraries*/
#include <stdio.h>
#include <stdlib.h>
/**functions prototypes*/
void main();
void function1();
int main(){
//main code of the program
return 0;
}
void function1(){
//function1 code
}
NextComments.

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Comments.
/*
……………
……………
Multi-line comment
……………..
……………..
*/
// single row comment
• Ignored by compiler.
• Can place any where.
Next#include macro.
.

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#include macro.
•It is used to include header files in our project.
•It may include constants, functions , declarations.
•#include reads the content of header file.
•#include <header.h> searches for a header file in the include
path.
•#include “header.h” searches for a header file in the current
directory for main project.
Next Variables in C.
.

Variables in C.
 Variable names are names given to locations in memory.
 Rules for Constructing Variable Names:
oA variable name is any combination of 1 to 31 alphabets ”compiler based”
oThe first character in the variable name must be an alphabet or
underscore.
oNo commas or blanks are allowed within a variable name.
oNo special symbol other than an underscore.
Examples:
int student_num;
char _student_num;
int 22student-num;
char student,num;
int student@num;
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Practical Advice:
It is a good practice to exploit
this enormous choice in naming
variables by using meaningful
variable names.
Next declare a variable in C.
.

How to declare a variable in C?
<Data Type> <variable name>;
<Data Type> <variable name> = <initial value>;
Examples:
//variable declaration with no initialization.
int student_num;
//variable declaration with intiial value.
char student_num=15;
//multiple variable declaration.
int num,student,id;
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Note:
If you don't initiate the variable it will take garbage value.
Next Variables in C.
.

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C data types:
Note:
You can use sizeof() function to
know the default size of variable.
EX:
Printf(“%d”,sizeof(int));
Practical Advice:
In E.S you should take care for
choosing the best suitable to
avoid wasting memory.

14
C data type Modifiers:
Note:
Signed modifier is the default modifier for any data type.
EX:
Signed char x=char x;

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Type Casting.
Type casting is to put variable in different type during run time.
Example:
int main ()
{
char x;
int y;
X=(char)y;
}
Note:
Some C compilers my give warning if assigned large data types values to small
data types values without using casting.
int main ()
{
char x;
int y=40000;
x=(char)y;
printf(“%d”,y);
printf(“%d”,x);
}
Try this !!!!!!

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printf.
To print constants :
printf(“Hello World !”);
To print variables:
Int x=50;
Float y=5.6;
Printf(“x is equal %d”,x);
Printf(“x is equal %d and y is equal %f”,x,y);
Format Specifiers:

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scanf.
To receive an input from user:
int x;
printf(“plz enter x value”);
scanf(“%d”,&x);
Hands ON
Write a C program to print “Hello World!”
Declare to variables and ask user to assign their values.

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Operators & Expressions.
Expression: it is a statement which an operator links identifiers.
Operators: they are some symbols that indicate to the compiler which type of
Operator is to be performed using its surrounding identifiers.
 Arithmetic Operators.
 Relational Operators.
 Logical Operators.
 Bitwise Operators.
 Assignment Operators.

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Arithmetic Operators.
Note:
• (%) is used only with integers.
• (++) and (- -) increment or decrement by one not add or subtract one   .
Assume variable A holds 10 and variable B holds 20.

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Example:
#include <stdio.h>
main()
{
int a = 21;
int b = 10;
int c ;
c = a + b;
printf("Line 1 - Value of c is %dn", c );
c = a - b;
c = a * b;
c = a % b;
c = a++;
printf("Line 2 - Value of c is %dn", a++);

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Relational Operators.
Relational operators are used in decision making and loops in C programming.
Note:
• If the relation is true, it returns value 1 and if the relation is false, it returns value 0.
• Don't be confused between (=) and (==).

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Examples:
#include <stdio.h>
main()
{
int a = 21;
int b = 10;
int c ;
if( a == b )
{
printf("Line 1 - a is equal to bn" );
}
else
{
printf("Line 2 - a is not equal to bn" );
}
}

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Logical Operators.
Note:
Don't be confused between (&&) and (&) or (||) and (|).

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Examples:
int a=5;
int b=6;
if (a && b) printf(“true”);
if (a || b) printf(“true”);
int x=0;
int y=5;
if(x && y++)
{
printf (“falsen”);
printf(“%d”,y);
}
Take Care!!
int x=0;
int y=5;
if(y || x++)
{
printf (“truen”);
printf(“%d”,x);
}

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Bitwise Operators.
Bitwise operator works on bits and perform bit-by-bit operation.

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Control single bit in Register or Byte:
 Reset one bit.
REG &=~(1<<bit_no)
PORTA &=~(1<<5)
 Toggle one bit.
REG ^=(1<<bit_no)
PORTA ^=(1<<5)
 Set one bit.
REG |=(1<<bit_no)
PORTA |=(1<<5)
Examples:
 Check one bit.
REG &=(1<<bit_no)
PORTA &=(1<<5)

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Decision Making.
 If statement.
if (condition)
{
}
else if (condition)
{
}
else
{
}

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Decision Making.
Switch (var)
{
Case 1:
statement;
break;
Case 1:
statement;
break;
Case 1:
statement;
break;
default:
statement;
break;
}

Email: mo7amed.fawzy33@gmail.com
Phone: 01006032792
Facebook: mo7amed_fawzy33@yahoo.com
Contact me:
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C programming day#1

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C programming day#1