Parallel port output
Usually in this situation I keep a variable with the whole byte, change the bits I want and then write it back to the port.

Example in C:

PortValue = 0x00;    // Set all bits to 0
LPT = PortValue;

PortValue |= 0x01;   // Set the bit 0 to 1
LPT = PortValue;

PortValue &amp;= ~0x01;  // Set the bit 0 to 0
LPT = PortValue;