A bitmap is a data structure in memory that represents information in the form of a collection
of individual bits. The following gives an explanation of how to determine and use bit values
in a bitmap.
A bitmap is a set of bits with a single bit representing a 0 or a 1:
0 0 0 0 0 0 0 0 - Bitmap with all bits set to zero
Bits are numbered from right to left in a bitmap. Starting first with the far right bit, it is bit
number 0. The next bit to the left is bit number 1, the next bit to the left of that one is bit
number 2, etc.
0 0 0 0 0 0 0 0 - Bitmap with all bits set to zero
7 6 5 4 3 2 1 0 - Bit numbers
Starting from bit number 0, each bit has a value that is half the value of the bit on its
immediate left (the bit value is not the same as the bit number). Bit number 0 has a value of 1,
bit number 1 has a value of 2, bit number 2 has a value of 4, bit number 3 a value of 8, and
so on:
0 0 0 0 0 0 0 0 - Bitmap with all bits set to zero
7 6 5 4 3 2 1 0 - Bit numbers
128 64 32 16 8 4 2 1 - Bit values
Each bit in a bitmap can be used to represent one subtest in a test category or a device in the
computer system, and with them you can indicate those features or devices that you either do
or do not want to use. For example, in the PCDR.INI file a bitmap can specify specific
subtests of a test category that you do not want to run in a test set. Or, with the /RT:
command line switch, a bitmap can specify multiple devices in a system (i.e., 4 hard drives or
4 serial ports) that you do want to run. Multiple subtests or devices are usually designated
with the first one equal to 0 rather than 1. Therefore bit number 0 represents the first subtest
or device, bit number 1 represents the second subtest or device, bit number 2 represents the
third subtest or device, et cetera.
0 0 0 0 0 0 0 0 - Bitmap with all bits set to zero
7 6 5 4 3 2 1 0 - Bit numbers
128 64 32 16 8 4 2 1 - Bit values
7 6 5 4 3 2 1 0 - Subtest or device IDs
To specify a subtest or device for whatever purpose, its assigned bit can be set to a 1.
Depending on how the bitmap is used, it can indicate subtests to exclude from running, or
devices to include for testing. For example, using the bitmap in the PCDR.INI file, to indicate
that you do not want to run the first and third CPU subtests their assigned bits (bits 0 and 2)
are set to 1. But used with the /RT switch, a bitmap can specify in a system with 4 hard disk
drives that you do want to run the first drive (device 0) and the third drive (device 2) by setting