case of else

Currently, Mad Pascal only accepts types with a length of 1 byte for the CASE variable: SHORTINT BYTE CHAR BOOLEAN.

case a of               // for a variable A of type CHAR
  'A'..'Z': begin end;
  '0'..'9': begin end;
  '+','*': begin end;

if then else

IF conditional instructions can be nested. This is used for more complex conditions.


for to downto do

FOR variable := { initial value } TO { final value } DO { instructions to execute }
FOR variable := { final value } DOWNTO { initial value } DO { instructions to execute }

This instruction is used to organize calculations which are performed a predetermined number of times. The control variable shall be an identifier of the ordinal type and both expressions shall be consistent in terms of assignment with the control variable type. During the TO loop execution, the control variable is assigned the subsequent value in the given type, in the DOWNTO loop, the preceding one. It is prohibited to "manually" change the value of a control variable. In case of such an attempt, MP signal an error Illegal assignment to for-loop variable.

The compiler makes sure that there is no endless loop so that you can use such a loop without a doubt:

for i:=0 to 255 do writeln(i);    // for a variable I of type BYTE

for in do

    FOR variable IN array DO { instructions to execute }
    FOR variable IN 'string literal' DO { instructions to execute }

The FOR IN DO construct allows for faster reading of array elements or text constants.

    days : array [0..6] of string =
    ('poniedzialek', 'wtorek', 'sroda' ,'czwartek', 'piatek', 'sobota', 'niedziela');

    a: string;

      for a in days do writeln(a);

while do

while { condition } do { instructions to execute }

This construct is used to organize calculations that will be performed as long as the expression after the word WHILE is true. Such a loop may not be executed even once.

while BlitterBusy do;   // waiting for the VBXE blitter to finish

Limitations for WHILE instructions:

while i<=255 do inc(i); // endless loop if I is of type BYTE

repeat until

  { instructions to execute }
until { termination condition }

This statement cyclically executes other statements between REPEAT and UNTIL until the expression after UNTIL takes the value of TRUE.

The effect of the REPEAT loop is very similar to that of the WHILE loop. This loop can also be performed a huge number of times. The only difference is that in the REPEAT loop the end condition is only checked after the instruction is executed. This means that the REPEAT loop will always be done at least once. Only after this iteration will the program check if the loop can be terminated. In the case of the WHILE loop, the condition is checked immediately before it is executed, which may result in the loop never being executed.

until i=0;      // the loop will repeat 256 times