This section reviews some classic machines from the history of automated computing devices and focuses on the major advances each embodied. Babbage's Analytical Engine is included here because of the many leaps of genius contained in its design. The other systems are discussed because they embodied significant technological advances and performed substantial real-world work over their lifetimes.

Charles Babbage's Analytical Engine

Although a working model of the Analytical Engine was never constructed, the detailed notes Charles Babbage developed from 1834 until his death in 1871 described a computing architecture that appeared to be both workable and complete. The Analytical Engine was intended to serve as a general-purpose programmable computing device. The design was entirely mechanical and was to be constructed largely of brass. It was designed to be driven by a shaft powered by a steam engine.

Borrowing from the punched...

For those working in the rapidly advancing field of computer technology, it is a significant challenge to make plans for the future. This is true whether the goal is to plot your own career path or for a giant semiconductor corporation to identify optimal R&D investments. No one can ever be completely sure what the next leap in technology will be, what effects from it will ripple across the industry and its users, or when it will happen. One technique that has proven useful in this difficult environment is to develop a rule of thumb, or empirical law, based on experience.

Gordon Moore co-founded Fairchild Semiconductor in 1957 and was later the chairman and CEO of Intel. In 1965, Moore published an article in Electronics magazine in which he offered his prediction of the changes that would occur in the semiconductor industry over the following ten years. In the article, he observed that the number of formerly discrete components such as transistors, diodes,...

The descriptions of a small number of key architectures from the history of computing mentioned in the previous section included some terms that may or may not be familiar to you. This section will provide an introduction to the building blocks used to construct modern-day processors and related computer subsystems.

One ubiquitous feature of modern computers is the use of voltage levels to indicate data values. In general, only two voltage levels are recognized: a low level and a high level. The low level is often assigned the value zero and the high level assigned the value one. The voltage at any point in a circuit (digital or otherwise) is analog in nature and can take on any voltage within its operating range. When changing from the low level to the high level, or vice versa, the voltage must pass through all voltages in between. In the context of digital circuitry, the transitions between low and high levels happen quickly and the circuitry is designed...

This chapter began with a brief history of automated computing devices and described significant technological advances that drove leaps in computational capability. A discussion of Moore's law was followed with an assessment of its applicability over previous decades and implications for the future. The basic concepts of computer architecture were introduced through a discussion of the 6502 microprocessor. The history of computer architecture is fascinating, and I encourage you to explore it further.

The next chapter will introduce digital logic, beginning with the properties of basic electrical circuits and proceeding through the design of digital subsystems used in modern processors. You will learn about logic gates, flip-flops, and digital circuits including multiplexers, shift registers, and adders. It includes an introduction to hardware description languages, which are specialized computer languages used in the design of complex digital devices such as computer...

1. Using your favorite programming language, develop a simulation of a single-digit decimal adder that operates in the same manner as in Babbage's Analytical Engine. First, prompt the user for two digits in the range 0-9: the addend and the accumulator. Display the addend, the accumulator, and the carry, which is initially zero. Perform a series of cycles as follows:

   a. If the addend is zero, display the values of the addend, accumulator, and carry and terminate the program.

   b. Decrement the addend by one and increment the accumulator by one.

   c. If the accumulator incremented from nine to zero, increment the carry.

   d. Go back to step a.

   Test your code with these sums: 0+0, 0+1, 1+0, 1+2, 5+5, 9+1, and 9+9.

2. Create arrays of 40 decimal digits each for the addend, accumulator, and carry. Prompt the user for two decimal integers of up to 40 digits each. Perform the addition digit by digit using the cycles described in Exercise 1, and collect the carry output from...