C Programming
Computers can understand only machine language which is written in Binary Digits i.e. zero (0) & one (1). But instruding computers through machine language will be very diffault as we have to give instuction in machine language. However there is a easier way of instructing computers. This is done through High Level Languages High Level Languages use simple words in English to instruct computers. The following are High Level Langugages Basic, Cobol, Pascal, C, etc.
The C Language has been around for quite some time & has seen the introduction of newer programming languages like Java, C++ & C#. Many of these new languages are dribed, at least in part from C, but are much larger in size. The more compact C is better to start out in programming because it is simpler to learn.
It is easier to learn the newer languages one the principles of C Programming have been grapsed. For instance, C++ is an extension of C & can be difficult to learn unless you have learnt C programming first.
Introduction to C Programming
The main() function
CHAPTER 3
Integer Format Specifier
Using Scientific Notifications
Variables:
In C the word identifier is used for names given to variables, functions etc.Rules for naming Variables
The First character in the identifier must be an alphabet. An identifier can contain alphabets & underscore. An identifier can contain both upper case and lower case alphabets (i.e. capital and small alphabets). An identifier Age and age are two different identifiers.
The Following are valid identifiers to name variables.
age, C5, height_a
The following are invalid identiers to name variables.
height * Characters other than alphabets
numbers, _ not allowed
float reserved word
4x first character is not an alaphabet
Data Types:
Declaring variables
If you have more than one variable to declare, you can use
e.g.
Assigning values to a variable
What will be the output of the following?
main()
{
int n1;
n1=52.0/10;
printf("The division of 52.0/10 is: %d\n", n1);
return 0;
}
main()
{
int n1;
n1=52/10.0;
printf("The division of 52/10.0 is: %d\n", n1);
return 0;
}
main()
{
float n1;
n1=52.0/10;
printf("The division of 52.0/10 is: %f\n", n1);
return 0;
}
#include
main()
{
float n1;
n1=52/10.0;
printf("The division of 52/10.0 is: %f\n", n1);
return 0;
}
#include
Arithmetical Operators
Exercises
4. Write a program to add two number 6 and 7(a=6 and b =7)
CHAPTER 4
HANDLING INPUT AND OUTPUT
e.g. printf("This is my first program");
the format string is This is my first program and there are no variables. After displaying the message, the cursor will remain at the end of the string. If we want to move the cursor to the next line, we should write
printf("This my first program\n");
Other examples of printf function
printf("The value of a is %d",a);
print the value of a has to be displayed as an integer.
printf("The value of a is %d, b is %f", a,b);
prints the value of a as integer & b as a decimal fraction.
Solved Example
/* to print characters*/
#include
main()
{
char a1, b1;
a1 ='x';
b1='y';
printf("The first character is %c\n", a1);
printf("The second character is %c\n",b1);
return 0;
}
/*to print numeric values of characters*/
#include
main()
{
char a1,b1;
a1='a';
b1='A';
printf("The value of first character is %d\n",a1);
printf("The value of sencond character is %d\n",b1);
return 0;
}
Note:- All the characters are stored in the form of bits(binary digits i.e. a combination of 0's and 1's.) Therefore each character has a unique numeric value to identify. Theref0re a and A are not equal and have a different numeric value. In the ASCII set there are unique numberic values for 255 characters.
/* to print the sum of two numbers*/
#include
main()
{
int a1, b1;
a1=10;
b1=20;
printf("The Sum of %d & %d is %d\n", a1, b1, a1+b1);
return 0;
}
Specifying the Minimum Field Width
You can add an integer between the % sign and the letter to specify the minimum field width. The integer is called the minimum field width specifier. For e.g. %5f makes sure that the output is 5 character spaces wide.
#include
main()
{
int a,b;
a=25;
b=1000;
printf("%d\n",a);
printf("%d\n",b);
printf("%5d\n",a);
printf("%05d\n",a);
return 0;
}
The first lines print normally. The third line %5d specifies 5 character spaces therefore three blank spaces are printed before 25.
You can also put a dot and an integer after the minimum width specifier to specify the number of decimal places for floating point numbers or to specify the maximum field width for integers.
#include
main()
{
int num=1;
printf("Using %%0d displays %0d\n",num);
printf("Using %%1d displays %1d\n",num);
printf("Using %%2d displays %2d\n",num);
printf("Using %%3d displays %3d\n",num);
printf("Using %%4d displays %4d\n",num);
printf("Using %%05d displays %05d\n",num);
printf("Using %%06d displays %06d\n",num);
printf("Using %%07d displays %07d\n",num);
return 0;
}
A program can ensure that output occupies a specific minimum number of spaces by specifying the required number in the format specifier. The number must be placed immediately after the % character in the format specifier. For instance, to ensure that an integer always fills at least 7 spaces the format specifier is %7d.
If it is preferable for the blank spaces to be filled with zeros just add a zero between the % character and the specified number. To ensure that an integer always fills at least 7 spaces and that any blank spaces are filled with zeros the format specifier is %07d.
#include
main()
{
float number = 7.123456;
printf("%-8.0f end\n",num);
printf("%-8.2f end\n",num);
printf("%-8.4f end\n",num);
printf("%-8.6f end\n",num);
return 0;
}
Greater control over the output appearance of floating point numbers can be gained by adding a precision specifier to the %f format specifier. This is simply a full stop followed by a number representing the desired number of decimal places to be displayed. For instance, a format specifier, of %2f will display a floating point number showing just 2 decimal places.
The minimum space specifier, described on the opposite page, can be combined with the precision specifier so that both number of minimum spaces and number of decimal places can be controlled. For instance, a format specifier of %07.2f decimal places, and any empty spaces would be filled with zeros.
By default, any empty spaces precede the number so it is right aligned. To have the number displayed left aligned, with any empty spaces added after the number, prefix the minimum space specifier with a minus sign as in the example above. The 'end' strings are just there to show that empty spaces have been added.
%8.3f means the minimum field width for floating point is 8 characters with 3 decimal places.
%2.7d means the minimum field width for integers is 2 and maximum field width is 7.
#include
main()
{
int a;
float b;
a=55;
b=22.222;
printf("%d\n",a);
printf("%2.7d\n",a);
printf("%f\n",b);
printf("%8.3f\n",b);
return 0;
}
Scanf Function
Till now, we have assigned values to variables within the program. Suppose we want to input the values during program execution, we can use the scanf() function. The general format of the input statement.
scanf(format-string, var1, var2....);
where format-string gives the information about the type of data and var1, var2.......gives the information about the number of variables.
For example, if you want to add any two numbers entered by the user, you would accept the two values by the statement.
scan("%d%d", &a,&b);
The two values will be stoered in the variables a and b. When you enter the two values they are to be seperated by a blank.
e.g. if you want to enter the two values 5 and 7, you will type it as 5 7. Similarly if you want to enter floating point numbers you type
scanf("%f %f",&a,&b);
The 'scanf()' function can be used to get in put into a program and it requires two arguments. First a formal specifier defines the type of data to be entered, then the name of the a variable in which the input will be stored. The variable name must be preceded by a '&' character, except when the data being entered is a string of text. The & character in this case, is the address of' operator that directs the input to be stored in the variable name that it precedes.
The scanf() function can set the value of multiple variables simultaneously too. The first argument must then contain a list of required format specifiers, each seperated by a space, and the entire list should be exclosed by double quotes. The second argument must contain a comma-seperated list of variable names to which each specified format applies.
#include
main()
{
char character;
int a,b;
printf("Enter anyone keyboard character\n");
scanf("%c",&character);
printf("Enter 2 integers seperated by a space\n");
scanf("The letter entered was %c\n",character);
printf("The letter enetered were %d and %d\n", a,b);
return 0;
}
#include
main()
{
int eng, hin, mar, maths, sc, ss;
printf("Enter the marks\n");
scanf("%d %d %d %d %d %d", &eng, &hin, &mar, &maths, &sc, &ss);
printf("\n Subjects English Hindi Marathi Maths Science Soc. Studies\n");
printf("Marks %d %d %d %d%d %d\n", eng, hin, mar, maths, sc, ss);
return 0;
}
Exercise
1. Write a program to input three number and print them on different lines
2. Write a program to input the marks of 6 subjects and print the total
3. Write a program to input the marks of 6 subjects and print the average
4. Write a program to input two alphabets and print it.
CHAPTER 5
DATA TYPE QUALIFIERS
When an int variable is declared it can by default contain either positive of negative integer values. The range of possible values is determined by your system.
If the int variable is created by default as a 'long' type it typically will have a possible range of values from a maximum of +2147483647 down to a minimum of -2147483648.
On the other hand, if the int variable is created by default as a 'short' type then typically the maximum possible will be +32767 and its minimum will be -32768.
The size can be specified when declaring the variable using the short and long keywords, as demonstrated in the code fragement:
short int num1; /* saves memory space*/
long int num2; /* allows bigger range*/
The limits.h header file contains implementation defined limits for the size of each data type. These are accessed via 'constant' values called INT_MAX and INT_MIN, for int variable declarations that do not specify a size. Similarly, SHRT_MAX and SHRT_MIN for short in variable declarations and LONG_MAX and LONG_MIN for long int variable declarations.
#include
#include
main()
{
printf("Max int: %d\t", INT_MAX);
printf("Min int: %d\n", INT_MIN);
printf("Max short:%d\t", SHRT_MAX);
printf("Min short:%d\n", SHRT_MIN);
printf("Max long:%d\t", SHRT_MAX);
printf("Min long:%d\n", SHRT_MIN);
return 0;
}
A non-negative 'unsigned' int can be declared with the unsigned keyword. An unsigned short int variable will typically have a possible range from 0 to 65535. An unsigned long int variable will typically have a possible range from 0 to 4,294,967,295.
The sizeof operator is used in this example to examine the amount of memory space allocated to various data types:
#include
main()
{
printf("Short int: %d bytes\t", sizeof(short int));
printf("Long int: %d bytes\n", sizeof(long int));
printf("unsigned long int:%d bytes\n", sizeof(unsigned long int));
printf("char: %d bytes \t", sizeof(char));
printf("float: %d bytes\t", sizeof(float));
printf("double: %d bytes\t\n", sizeof(double));
return 0;
}
CHAPTER 6
EXTERNAL VARIABLES
The extent to which a variable is accessible in a program is called the ‘variable scope’. Variables declared internally inside a function are known as ‘local’ variables, whereas variables that are declared externally outside a function are known as ‘global’ variable.
Local variables can only be accessed by the function in which they are declared. They come into existence when the function is called and normally disappear when the function is exited.
Global variables on the other hand can be accessed by all functions in a program. They remain in existence permanently so are useful to communicate data between functions.
An external global variable must be defined exactly once at the start of the program. It must also be declared at the start of each function that wants to use it. Each declaration should begin with the extern keyword which denotes that it is for a global variable, rather than for a regular local variable. These declarations should not be used to initialize the global variable.
The example below demonstrates has to define declare and initialize an external global variable called ‘num’.
#include
int num; /*define an external variable*/
main()
{
extern int num; /*declare the external variable*/
num =5;
printf(“Global variable value is %d”, num);
return 0;
}
CHAPTER 7
STATIC VARIABLES
Larger C Programs consist of multiple source code files that are compiled together to create a final executable file. This is a very useful aspect of C Programming that allows source code to be modular so that it can be reused in different programs.
Global external variables, as described on the opposite page, would normally be accessible to any function in any of the files being compiled together. All functions are normally accessible globally too. Functions and, more usually external variables can have their accessibility limited to just the file in which they are created by the use of the static keyword.
Normally a program cannot employ more than one variable of any given name. Using static external variables, however, usefully allows external variables of the same name to coexist happily providing they are declared as static and are not in the same file. Programming with multiple source code file. Programming with multiple source code file can find a common external variable name duplicated in two files. Declaring these as static avoids the need to rename one of these variables in each occurence within the source code.
The example below creates a static global external variable that cannot be used by other source code files. Attempting to do so causes an error at compile time and the compilation will halt.
#include
static int num=100; /*define static external variable*/
main()
{
extern int num; /* declare the external variable*/
printf("Global variable: %d", num);
}
CHAPTER 8
MANIPULATING DATA
Arithmetic Assignment Operators:-
We have already worked with the assignment operator =. The value on the right hand side of the = operator is assigned to the variable on the left of the = operator.
e.g. x=a+b
or y=50+10
or z=20
In the above case, the value of a+b is assigned to the memory location x
or y is assigned the value 60
or 20 is stored in the memory location z.
Similarly, the statement x=y=10 assigns 10 to the integer variable y and then to integer variable x. After the execution of the statement
The expression works from right tor left therefore the expression 10=x will not work.
Now consider the expression x=x+y. The operator always works from right to left, so on the side the addition of x+y is executed and on the left side of =, the previous value of x is replaced by addition of x and y on the right side.
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