Delphi Programming/Operators, structures and loops
The if-structure 
The if-structure executes a block of commands if a boolean expression returns True. A more simle to understand explanation is: It executes a block or a single command if a condition is true. Example:
begin if a = False then WriteLn('a is false') else WriteLn('a is true'); end.
Never write "if a = True" but simply write "if a". Writing "if a = False" is correct, but you can also write "if not a" or (with brackets) "if (((((a)))))" (or as many brackets you want), also "(if (not(a)))".
begin if CONDITION then DO_ANYTHING else DO_THIS; end.
or (for more than one command to execute):
begin if CONDITION then begin DO_ANYTHING; end else begin DO_THIS; end; end.
Or without the else:
begin if CONDITION then begin DO_THIS; end; end.
Except the last end there's always a semicolon behind the end. There is never a semicolon before an "Else"!
var _Answer: string; begin WriteLn('Do you want to order a pizza?'); ReadLn(_Answer); if _Answer = 'Yes' then WriteLn('You decided for yes!') else WriteLn('Don''t want to have a pizza?'); end.
With '' in a string you can put ' out (because of a single ' would close the string). For '' Write '''' (or with the start and end chars '''''').
The case structure 
The Case structure is quite similar to the if structure with the following difference: You can easier ask for several cases!
case VARIABLE_NAME of VALUE_1: DO_THIS; VALUE_N: DO_THIS else DO_THIS end; end;
But with a case-structure you can only ask for Integers and chars.
Expanding the condition 
You can expand your condition with a few operators:
- AND (C: &): bitwise 'and': if (a = 1) and (b = 2). The value of the expression "(a = 1) and (b = 2)" is TRUE if a is 1 and b is 2. Else, the value is FALSE and the ELSE-part will be executed (and not the part after THEN). Don't forget the brackets!
- OR (C: |): 'or': if (a = 1) or (b = 1). If a is 1, b is 1 or both is 1, the value of the expression is TRUE.
- XOR: If only one of the conditions is true: if (a = 1) xor (b = 2). The expression is true if a is 1 or b is 2. If a is 1 AND b is 2, the value will be FALSE!
- NOT: The opposite of the expression.
It's also possible to interlink that operators. But then don't forget the brackets!
By the way: Every condition returns a boolean value. If it is TRUE, the then-part will be executed. If not, the processor goes to the else-part.
Operators such as 'equals' 
Operators such as '=' are:
- = - equals
- > - greater than
- < - less than
- <= - less or equals
- >= - greater or equals
- <> - less or greater (but not the same)
Operators for calculating 
- You can use ( and ) as brackets.
- / means 'divided by', the result is a float
- div means 'divided by', the result is a rounded integer
- * means 'times'
- + means 'plus'
- - means 'minus'
+ also means linking of strings or chars:
- string + string : string
- string + char : string
- char + char : string
- char + string : string
- string + number : error
- number + string : error
- number + number : number
- number + char : error
- char + number : error
Loop means: A block will be executed many times. There are four types of loops:
for [var] := [start] to [end] do begin [execute the following code] end;
The var will count from [start] to [end] and after every counting step the code will be executed. Normally the [var] is defined as i, j or k, but you can also choose counting_var_with_this_name or any name.
for [var] := [start] downto [end] do begin [execute the following code] end;
The var will count down from [start] to [end] and after every counting step the code will be executed.
while [condition] do begin [code] end;
While the condition is true, the code will be executed. Whether the condition is TRUE or FALSE will be checked BEFORE executing the code.
repeat [code] until [condition];
The code will be executed until the condition is true. Whether the condition is TRUE or FALSE will be checked AFTER executing the code.
Setting values 
The operator for setting values is :=
a := b;
By executing, a will get the value of b.
a equals 1; b equals 3
a equals 3; b equals 3
a equals 1; b equals 1
Be careful with the order!