C Programming course for beginners and intermideate

Array Programming in C
Studying C Coding from Embedded System Perspective

Character Array
in C
Strings and Char operations for
embedded systems

Char
Every printable
character is
represented by
its ASCII Code
01
ASCII code is
max 7 bit long
02
unsigned or
signed char
can be used
03
An array of
char variables
is also called
string
04

Printing a char
%c can be used with printf to print a single char
putchar can be used to print a single char
%s can be used with printf to print a string
Puts can be used to print a string

How char is scanned
• When we scan a char using %c directive, then the
decimal equivalent of the character that you
entered is saved in the variable
• When you print it using %c directive, then the
decimal number is “AS IS” sent to print buffer, and
since it resemebles an actual ascii code of a letter,
the letter is printed.

Scan ( input
a char)
Single char can be input with scanf function using %c
single char can be input with getchar function
String can be input with scanf function using %s
String can be input with gets function
None of scnaf / printf / getchar / gets / puts / putchar
functions are available in Embedded Systems

Character Comparison
char my = ‘a’
if(my == ‘a’)
{
}

String Comparison
char a[10] = “welcome”
if(strcmp(a, “welcome”) == 0)
{
}

String Functions
in C ( also
available in all
embedded
systems)
Sr.No. Function & Purpose
1 strcpy(s1, s2);
Copies string s2 into string s1.
2 strcat(s1, s2);
Concatenates string s2 onto the end of string s1.
3 strlen(s1);
Returns the length of string s1.
4 strcmp(s1, s2);
Returns 0 if s1 and s2 are the same; less than 0 if s1<s2; greater than
0 if s1>s2.
5 strchr(s1, ch);
Returns a pointer to the first occurrence of character ch in string s1.
6 strstr(s1, s2);
Returns a pointer to the first occurrence of string s2 in string s1.

sprintf
Convert float/int to string in Embedded C

Pointers in C
Very important for Embedded Systems

Pointer Syntax in Declaration
int *a;
int *p;

Assigning addresses to Pointers
“Address of”(&) Operator
int *p
int c;
c = 5;
p = &c;

Get Value of Thing Pointed by Pointers
“Value at Address”(*) Operator
int *p;
int c;
c = 5;
p = &c;
printf("%d", *p); // Output: 5

Functions
Codes that need to
repeat
Function without any
argument
Function with one or
more argument
Function that returns one
argument

Function Syntax
Function_datatype function_name(arguments)
{
return arguments_if_any
}

Functions to return
multiple values
• Using pointers to return multiple
values
• Pass on the address of variables
function_name(&a, &b)
• Write on these values

Global and Local
Variables
C Functions demystified

Array Argument
in Function
How to Pass an array to function in C

Function to
Accept char array
and String

switch
switch (expression)

{
case constant1:
// statements
break;
case constant2:
// statements
break;
.
.
.
default:
// default statements
}

How switch
case is
executed
• The expression is evaluated once and
compared with the values of each case label.
• If there is a match, the corresponding
statements after the matching label are
executed.
• For example, if the value of the expression is
equal to constant2, statements after case
constant2: are executed until break is
encountered.
• If there is no match, the default statements
are executed.

Preprocessor
Directives
In C Coding

What are pre-processor directives?
• Basically a text substitution tool
• Begins with # symbol (remember #include )

Example
• stdio.h is a header file. The #include preprocessor directive replaces
the above line with the contents of stdio.h header file.
• You can also create your own header file containing function
declaration and include it in your program using this
preprocessor directive.
• #include “my_header.h”
• This file should be present in the same folder where your main c code
is placed

#define Substitutes a preprocessor macro.
#include Inserts a particular header from another file.
#ifdef Returns true if this macro is defined.
#ifndef Returns true if this macro is not defined.
#if Tests if a compile time condition is true.
#else The alternative for #if.
#elif #else and #if in one statement.
#endif Ends preprocessor conditional.
#error Prints error message on stderr.
#pragma Issues special commands to the compiler, using
a standardized method.

• #define MAX_ARRAY_LENGTH 20
• This directive tells the preprocessor to replace instances of
MAX_ARRAY_LENGTH with 20.
• We Use #define for constants to increase readability.

Define Macro using #define
• #define message_for(a, b) printf(#a " and " #b ": We love you!n")

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