As the name suggests the ‘Control Instructions’ enable us to specify the order in which the various instructions in a program are to be executed by the computer. In other words the control instructions determine the ‘flow of control’ in a program. There are four types of control instructions in C. They are:
(a) Sequence Control Instruction
(b) Selection or Decision Control Instruction
(c) Repetition or Loop Control Instruction
(d) Case Control Instruction
The Sequence control instruction ensures that the instructions are executed in the same order in which they appear in the program. Decision and Case control instructions allow the computer to take a decision as to which instruction is to be executed next. The Loop control instruction helps computer to execute a group of statements repeatedly. In the following chapters we are going to learn these instructions in detail. Try your hand at the Exercise presented on the following pages before proceeding to the next chapter, which discusses the decision control instruction.
Summary
The three primary constants and variable types in C are integer, float and character.
A variable name can be of maximum 31 characters.
Do not use a keyword as a variable name.
An expression may contain any sequence of constants, variables and operators.
Operators having equal precedence are evaluated using associativity.
Left to right associativity means that the left operand of a operator must be unambiguous whereas right to left associativity means that the right operand of a operator must be unambiguous.
Input/output in C can be achieved using scanf( ) and printf( ) functions.
