Every loop has four elements that are used for different purpose. These elements are
(i) Initialization expression
(ii) Test expression
(iii) Update expression
(iv) The body of the loop
(i) Initialization expression(s): The control variable(s) must be initialized before the control enters into loop. The initialization of the control variable takes place under the initialization expressions. The initialization expression is executed only once at the beginning of the loop.
(ii) Test Expression: The test expression is an expression or condition whose value decides whether the loop-body will be executed or not. If the expression evaluates to true(i.e., 1), the body of the loop executed, otherwise the loop is terminated. In an entry-controlled loop, the test-expression is evaluated before the entering into a loop whereas in an exit-controlled loop, the test-expression is evaluated before exit from the loop.
(iii) Update expression: It is used to change the value of the loop variable. This statement is executed at the end of the loop after the body of the loop is executed.
(iv) The body of the loop: A statement or set of statements forms a body of the loop that are executed repetitively. In an entry-controlled loop, first, the test-expression is evaluated and . if it is nonzero, the body of the loop is executed otherwise the loop is terminated. In an exit controlled loop, the body of the loop is executed first then the test-expression is evaluated. If the test expression is true the body of the loop is repeated otherwise loop is terminated.

For loop: The for, loop is the easiest looping, statement which allows code to be executed repeatedly. It contains three different statement (initialization, condition or test-expression and update expression(s) separated by semicolons.
The general syntax is
for (initialization(s); test-expression; update expression( s))
{
Statement 1;
Statement 2;
}
Statement-x;
The initialization part is used to initialize variables or declare variable which are executed only once, then the control passes to test-expression. After evaluation of test-expression, if the result is false, the control transferred to statement-x. If the result is true, the body of the for loop is executed, next, the control is transferred to update expression. After evaluation of update expression part, the control is transferred to the test-expression part.
Example:
#include < iostream.h >
using namespace std;
int main ( )
{
int i;
for(i = 0; i < 10; i ++ )
cout << "value of i :" << i << endl;
return 0;
}
Output:
value of i : 0
value of i : 1
value of i : 2
value of i : 3
value of i : 4
value of i : 5
value of i : 6
value of i : 7
value of i : 8
value of i : 9

(i) Expression inside if statement decide whether to execute the statements inside if block or under else block. On the other hand, the expression inside a switch statement decides which case to execute.
(ii) An if-else statement uses multiple statements for multiple choices. On other hands, switch statement uses single expression for multiple choices.
(iii) If-else statement checks for equality as well as for logical expression. On the other hand, switch checks only for equality.
(iv) The if statement evaluates integer, charter, pointer or floating-point type or Boolean type. On the other hand, switch statement evaluates only character or integer data type.
(v) Sequence of execution is like statement under if block will execute or statements under else block statement will execute. On the other hand, the expression in switch statement decide which case to execute and if do not apply a break statement after each case it will execute till the end of switch statement.
(vi) If expression inside if turns out to be false, statement inside else block will be executed. If expression inside a switch statement turns out to be false then default statements are executed.
(vii) It is difficult to edit if-else statements as it is tedious to trace where the correction is required. On the other hand, it is easy to edit switch, statements as they are easy to trace.

Rules:
(i) The expression provided in the switch should result in a constant value otherwise it would not be valid.
(ii) Duplicate case values are not allowed.
(iii) The default statement is optional.
(iv) The break statement is used inside the switch to terminate a statement sequence. When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement.
(v) The break statement is optional, 'If omitted, execution will continue on into the next case. The flow of control will fall through to subsequent cases until a break is reached.
(vi) Nesting of switch statements is also allowed.