# Shl

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Back to Reserved words.

## Overview

The reserved word Shift left (shl) performs a left bit-shift operation, shifting the value by the amount of bits specified as an argument (opposite of shr).

Example:

```Command is: 00000100 shl 2 (shift left 2 bits)

Action is:  00000100 <- 00 (00 gets added to the right of the value; left 00 "disappears")

Result is:  00010000
```

## Clear a bit

```function ClearBit( const aValue, aBitNumber : integer ) : integer;
begin
// sanity check supplied value
if (aBitNumber <0) or  (aBitNumber >15) then
result :=0
else
// value ok
result := aValue and not( 1 shl aBitNumber );
end;
```

If you call ClearBit(%1111,1), then you get %1101 (The binary number %1111 is 15 and %1101 = 13).

If you call ClearBit(13,2), then you get 9 (9 = %1001).

In this case, bits are numbered right to left from 0 to 15, bit 0 being the ones bit and bit 15 being the sign bit.

operators `and` • `or` • `not` • `xor` `shl` • `shr` `and_then` (N/A)• `or_else` (N/A)