End of Chapter Summary

Whether it’s working with words, numbers, pictures, or sounds, a computer is manipulating patterns of bits—binary digits of information that it can store in switching circuitry and that are represented by two symbols. Groups of bits can be treated as numbers for calculations using the binary number system. Bits can be grouped into coded messages that represent alphabetic characters, pictures, colors, sounds, or just about any other kind of information. Even the instructions computers follow—the software programs that tell the computer what to do—must be reduced to strings of bits before the computer accepts them. Byte, kilobyte, megabyte, and other common units for measuring bit quantities are used in descriptions of memory, storage, and file size.

The microprocessor, or central processing unit (CPU), follows software instructions to perform the calculations and logical manipulations that transform input data into output. Not all CPUs are compatible with each other; each is capable of processing a particular set of instructions, so a software program written for one family of processors can’t necessarily be understood by a processor from another family. Engineers are constantly improving the clock speed and architecture of CPUs, making computers capable of processing information faster.

The CPU uses RAM (random access memory) as a temporary storage area—a scratch pad—for instructions and data. Another type of memory, ROM (read-only memory), contains unchangeable information that serves as reference material for the CPU as it executes program instructions.

The CPU and main memory are housed in silicon chips on the motherboard and other circuit boards inside the computer. Buses connect to slots and ports that enable the computer to communicate with internal devices and external peripherals.