Managing Information Technology

26 Part I • Information Technology

Operation Code Addresses

A 470 500

M 500 200

P 200

means the computer should add the number found in memory

cell 470 to the number found in memory cell 500, storing the

result back in memory cell 500. Therefore, if the value 32.10

is originally stored in cell 470 and the value 63.00 is originally

stored in cell 500, the sum, 95.10, will be stored in cell 500

after the instruction is executed. Continuing our example,

assume that the next instruction in the sequence is

This instruction means move (M) the contents of memory

cell 500 to memory cell 200. Thus, 95.10 will be placed in

cell 200, erasing whatever was there before. (Because of

nondestructive read-out, 95.10 will still be stored in cell

500.) The third instruction in our sequence is

Processor Chips

At the heart of every computer today is one or more processor chips,such as the Intel Core i7 processor

chip shown in Figure 2.4. It is important to note that the processor chip includes boththe

arithmetic/logic unit and the control unit. The Intel Core i7 processor chip, which is used in many of

today’s top-of-the-line microcomputers, contains hundreds of millions of transistors and has been

described by Intel as the “fastest processor on the planet” (Intel Web site, 2008). It is also a quad-core

processorwhich has four complete processors manufactured as part of a single chip.

Intel is not the only processor chip maker, but it is the largest and the most important. Intel sup-

plies over 80 percent of the microprocessor chips used to power microcomputers, with Advanced Micro

Devices (AMD) supplying most of the rest. Other manufacturers of processor chips (largely for more pow-

erful computers) include IBM and Sun Microsystems.^1 As an interesting side note, IBM also provides the

processor chips for all of the newest-generation game consoles (i.e., Sony, Microsoft, and Nintendo).

(^1) Sun Microsystems was acquired by Oracle in 2010.
FIGURE 2.4 Intel®Core™ i7 Processor (Courtesy of Intel
Corporation)
Not only will the form of the instructions vary from
one computer model to another but so will the number of
different types of instructions. For example, a small computer
may have only one add instruction, while a large one may
have a different add instruction for each of several classes of
numbers (such as integer, floating point or decimal, and dou-
ble precision). Thus, the instruction set on some machines
may contain as few as 20 types of instructions, while other
machines may have more than 200 instruction types.
In general, each machine language instruction
consists of two parts: an operation code and one or more
addresses. The operation code is a symbol (e.g., A for add)
that tells the control unit what operation is to be performed.
The addresses refer to the specific cells in memory whose
contents will be involved in the operation. As an example,
for a hypothetical computer the instruction
which means print (P) the contents of memory cell 200 on
the printer, and 95.10 will be printed.