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SharpBASIC has several statements to control the flow of a program. There is the conditional statement if, the comparison/switch statement when, and the loop statements for and loop.

An if statement tests a condition, which is a boolean expression, and executes the block following if the result of the boolean expression is true:

if x > 0
  do
    print(x);
  end

Note the delimiters do..end, which mark the block to be executed following the boolean expression. Unlike many programming languages, SharpBASIC does not have the keyword then.

Multiple if branches are possible with the keyword else:

if x == 1 do
  ' ..
else if x == 2 do
  ' ..
else if x == 3 do
  ' ..
else do
  ' ..
end

Although two keywords are used for an else if statement, it actually behaves like elseif, so this syntax does not result in nested if-statements. Nested statements are always within do..end blocks:

if x == 1 do
  ' ..
else do
  if x == 2 do
    ' ..
  end
end

The when-statement is similar to the if-statement, but instead of testing a condition, it compares an identifiers value to one or more expressions by means of is-branches:

when x
  is 1 do
    ' ..
  is 2 do
    ' ..
  is other do
    ' ..
end

The when-statement is similar to a switch statement in other languages. As such it supports fall-through, but only when explicitly stated:

when x
  is 1 do
    x = 2;
    fall;
  is 2 do
    ' ..
end

A mix of values and ranges can be tested per branch:

when x
  is 1 to 5, 7 do
    ' ..
  is 8 to 10 do
    ' ..
  is other do
    ' ..
end

The when-statement can be used to test a range similar to an if-statement, for example:

if a > 0 and a < 10 do
  ' ..
end

when a is 1 to 9 do
  ' ..
end

It is also possible to do an opposite or not-comparison:

when a is not 1 to 9 do
  ' ..
end

Another example where the when-statement can be used instead of an if-statement:

if x <> 0 and y <> 0 do
  ' ..
end
' versus
when null is not (x and y) do
  ' ..
end

The when-statement can only be used with identifiers. It cannot compare an immediate:

when 0 is not (x and y) do    ' ERROR
  ' ..
end

Because SharpBASIC translates all immediates into constants, it is good practice to define commonly used values as constants. Some values are predefined, such as true and false:

when true is not a < 10 do    ' equivalent to "if a >= 10 do"
   ' ..
end

The for-statement, commonly known in other languages as the 'for-loop' is a fixed loop that executes the specified number of times. In the following example the loop will run 10 times, whereby the variable i starts with value 0 and is incremented by 1 each time the loop is repeated:

for i = 0 to 9 :++ do
  ' ..
end

Note the operator :++, which tells the direction of the iteration. The direction can be up (increment operator) or down (decrement operator):

for i = 10 to 1 :-- do
  ' ..
end

When a for-statement has ended without interruption, the iteration variable will be the maximum value plus one after an incremental iteration and the minimum value minus one after a decremental iteration. However, if the value is not within the range of the iterator's data type, the value is rotated:

dim i: uitr;    ' unsigned
main do
  for i = 9 to 0 :-- do
    ' ..
  end
  print(i);       ' 4294967295
end

The loop-statement is SharpBASIC's variable loop:

loop do
  ' ..
end

In this form the loop would execute forever. Be careful! But SharpBASIC has some keywords to control the exit of a (variable) loop. The loop statement can be made conditional at the beginning with the keywords while and until:

loop do
  while x > 1;
  ' ..
end

loop do
  until x == 0;
  ' ..
end

Likewise, the loop can be made conditional at the end:

loop do
  ' ..
  while x > 1;
end

loop do
  ' ..
  until x == 0;
end

Note that the while and until condition statements are inside the do..end block. A condition statement at the beginning must always come before any other statement in a loop do ..end block. Similarly, a condition statement at the end must always be the last statement in a loop do ..end block. Both while and until are allowed at the beginning or at the end. However, only one condition statement is allowed.

Both the for-statement and the loop-statement can be influenced by the statements break and skip. The break-statement exits a loop unconditionally and continues the program with the first statement after the loop. The skip-statement immediately continues with the next loop skipping any remaining statements in a loop-block.

n = 0;
loop do
  n:++;
  ' exit loop if n is 10
  if n == 10 do
    break;
  end
  ' print empty line instead of 5
  if n == 5 do
    print();
    skip;
  end
  print(n);
end

SharpBASIC supports jumps to labels (label statements). Label statements are addresses for the jump statement to jump to. Labels must start with @ followed by a name consisting of letters and/or numbers and underscores.

jump @MyLabel;
' ...
@MyLabel;
' ...

Jump statements are only allowed in subroutines and functions.

In the following example, the jump statement is used to exit a loop-statement.

sub sub1()
  dim n:int = 0;
do
  loop do
    if n == 6 do
      jump @here;
    end
    n:++;
  end
  @here;
  print(n);
end

sub sub1()
  dim i, j, k:itr;
do
  for i = 1 to 9 :++ do
    for j = 1 to 5 :++ do
      for k = 1 to 3 :++ do
        if i == 6 do
          jump @final;
        end
      end
    end
  end
  @final;
  print(i);
end

The final way to exit a loop is with a return statement. In a subroutine return is used (without return value) to immediately exit the routine. In a function return can optionally return a value.

sub sub1()
  dim i,j,k:itr;
do
  for i = 1 to 3 :++ do
    for j = 1 to 4 :++ do
      for k = 1 to 5 :++ do
        if k == 3 do
          return;
        end
      end
    end
  end
end