course-c

if-else

• if-else expresses decisions

• else part is optional

  if (expression)
  statement1
  else
  statement2
  

• expression returns a numerical value
• 0 is considered FALSE, any other value is TRUE

if-else ambiguities

:::: {.columns}

::: {.column}

• By default, the else is associated with the inner if

  if (i >= 0)
    if (i < 5)
      a = b;
    else
      a = c;
  

:::

::: {.column}

• Use braces to remove ambiguity

  if (i >= 0) {
    if (i < 5)
      a = b;
  } else
    a = c;
  

:::

::::

else-if

• Useful for expressing multi-way decisions

  if (expression)
    statement
  else if (expression)
    statement
  else if (expression)
    statement
  else
    statement
  

switch

:::: {.columns}

::: {.column width=”40%”}

  switch (expression) {
    case const-expr:
      statements
    case const-expr:
      statements
    default:
      statements
  }

:::

::: {.column width=”60%”}

• Used to express multi-way decision

• Matches the result of an expression to one of several integer constants

• a break statement causes exit from the switch
• without a break all statements after the matching case are executed till the end of the switch block

:::

::::

while

• The while loop executes as long as expression is TRUE (not 0)

  while (expression) {
    statements
  }
  

for

• The loop has three parts

  for (expr1; expr2; expr3) {
    statements
  }
  

  • expr1 is an initialization expression
  • expr2 is a relational expression, and
  • expr3 is the increment expression

• The loop executes as long as expr2 is TRUE (not 0)

• All three expressions can be empty which leads to an infinite for loop

do-while

• The do loop executes at least once before expression is evaluated

  do {
    statements
  } while (expression);
  

• The loop executes as long as expression is TRUE (not 0)

break

• Using the break statement causes immediate exit from a loop (for, while or do-while) or switch block

continue

• The continue statement causes a loop to begin the next iteration, the statements following continue are not executed

goto

• the goto statement causes execution to jump to the statements after the label

  goto label;
  statements
  label:
  statements
  

• goto is not recommended as it results in spaghetti code

Exercise

• Write a program that converts 1 to 50 mile(s) into kilometers

  NOTE 1 mile = 1.609344 kilometers

• Print the result in tabular form

  01 mile(s) = 01.609344 km   02 mile(s) = 03.218688 km
  03 mile(s) = 04.828032 km   04 mile(s) = 06.437376 km