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Represent increment operator by a++ or ++a.

The meaning of the symbol ”~” is 1’s complement operator.

The value of 17%-2 is +1.

As the name implies Logical errors are related to the logic of the program execution. Logical errors do not show compiler generated error messages rather they cause wrong results. These errors are primarily due to poor understanding the problem, incorrect translation of the algorithm into program and lack of clarity of hierarchy of operators. In the statement if(x= =y) printf(“They are equal\n”); when x and y are float type, they rarely become equal due to truncation errors. The printf may not be executed at all. Similarly test condition while(x!=y) might create an infinite loop.

Logical AND is represented as &&, Logical OR as || and NOT as!

Relational operator is used to compare two operands in an expression.

(i) + addition or unary plus,

(ii) - subtraction or unary minus,

(iii) * multiplication,

(iv) / division,

(v) % modulo division.

The process of executing the program to test the correctness of the results is testing.

When the user tries to run ambiguous instructions run time error occurs. Errors of mismatching the data types, referencing out of range array element cannot be detected by the compiler. Divide by zero, data overflow are some examples.

Run time errors occur when the user tries to run ambiguous instructions.
(like infinite loop, divided by 0 etc)

Generally, programmers do three types of errors namely syntax error, logical error and run time error.

In writing a C program one style should be used and there should be consistency. Lower case letters are used to write a program. Group program statements are written together. Braces used to mark the beginning and end of the function. C is free from language, one can group statements together on same line. However, this make the program more difficult to understand.

The constants used in C are broadly divided as numeric and non numeric constants. Numeric is further divided as integer and float point constant, while non numeric is divided as character and string constants.

Program is executed in the central processing unit(CPU).

The quantity which does not change during the execution of a program is a constant.

The run time errors are infinite loop in a program, divide by zero, null pointer assignment, data overflow.

Floating constant is a number with a decimal point. It is a sequence of digits preceded and followed by a decimal point. General form of floating constant is sign integer part decimal point fractional part. Example is 28.75, -0.00002345, 0.123e5.

The basic and smallest units of a C program are C tokens.(keywords, constants, operators etc)

Keywords, identifiers, constants, strings, operators and special symbols are the different C tokens.

General format of scanf( ) formatted input is scanf(“control string”, address list).

To perform input-output operations C provides a library functions. This is called standard input-output library. It is denoted as stdio. Header file containing such library functions is stdio.h. scanf( ), printf( ), getchar( ), putchar( ), gets( ), puts( ), getch( ),getche ( ) are the standard functions in C performing i/o operations.

Function scanf( ) is used to read the values for the variables in C from the keyboard. The scanf( ) is used to enter the numeric, character and string type data. It is included in the header file <stdio.h>. C programming provides printf( ) function to display the data on the output device(monitor). Syntax for scanf( ) and printf( ) is printf(“control string”, variable); scanf(“control string”, address_list);