Basics of C language
Body of the C code for
embedded systems
#include<reg51.h>
\\ header file used for 8051
\\microcontroller
delay(unsigned int )\\
function prototype
void main() \\ initializing the main
function
{
P1=0x00; \\body of the
main
\\ program
delay(65000);
P1=0x0AA;
delay(65000);
}
delay(unsigned int x)
\\subroutine for delay function
{
unsigned int a;
\\variable declaration
a=x;
}
Loops used in C :
Super loop or forever loop:
while(1)
for(; ;)
This loop will run infinite time.
This loop is used to
repeat the same code infinite
times.
while(1) {
code which is repeated again and again.
}
for(; ;){
Statement
}
While loop:
The code written in this loop will run if until the
Condition is true.
For example:as used in delay function.
while(a!=0){
a--;}
This loop will run until a is non zero.
In embedded system
this loop is also used for waiting .
For example :
while(RI==0);
The MC will wait here until RI becomes 1.
For loop:
The body of the for loop is shown below.
for(i=0;i<10;i++)
{
{
statement;
}
Where i=0 –lower limit
i<10 – upper
limit
i++ - operation
if else statement:
This is the conditional statement .
The body of this statement is shown below.
if(statement 1)
{
Statement 2
}
{
Statement 2
}
else
{
{
Statement 3
}
}
In this case if statement 1 is true then statement 2 will run
or if it is not true then
statement 3 will run.
statement 3 will run.
Switch statement:
Switch is a multiway decision statement that tests
whether a expression matches one of a number of
whether a expression matches one of a number of
constant integer values.
Body of the switch statement is –
Switch(expression)
{
{
case1: statement 1
case2: statement 2
case3: statement 3
}
Arrays:
There are two types of arrays
1.one dimensional array
2.two dimensional array
1. One dimension array:
One dimensional array is
also known as string. Body of string is-
Unsigned char name of
the string[size of string]= “message”;
How to use string
in embedded system programing
is shown below-
void main()
{
unsigned char str[20]= “Manpreet
Singh Akali”;
unsigned char i;
for(i=0;i<20:i++){
P0=str[i];}
}
This program will send
the string to port 0.
2. Two dimension array:
Two dimension array
consists of rows and columns.
Unsigned char array[a][b]={‘a’,
‘b’, ‘c’,
‘d’, ‘e’, ‘f’,
‘g’, ‘h’, ‘I’};
To send any value to
port0 from this array we write
P0=array[a][b];
Where a,b are two integers
representing the row and column of the value in array.
Functions :
C language is a mid level
language with nhigh level features . It also supports the function .
For example:
strcmp(s1,s2):
this function is used to
compare two strings s1 and s2.
This function helps in setting the
password in embedded system applications.
For more details contact:
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