The computer's microprocessor reads in and handles a certain number of 0's and 1's at a time. For example, it may be designed to read 32 bits at a time. Because it is designed to know how many bits (and which bits) tell it what operation to do, it can look at the right sequence of bits and perform the next operation. Then it reads the next instruction, and so on.

   In analyzing problems or debugging programs, a tool to use is a dump of the program. A dump is a printout that shows the program in its machine code form, but since putting it in 0's and 1's would be hard to read, each four bits (of 0's and 1's) are represented by a single hexadecimal numeral. (Dumps also contain other information about the computer's operation, such as the address of the instruction that was being executed at the time the dump was initiated.)

   The Macintosh has its own operating system, Mac OS. Originally built on a line of Motorola microprocessors, Mac versions today are powered by the PowerPC microprocessor, which was developed jointly by Apple, Motorola, and IBM. The Mac is actually a line of personal computers, configured for individual users and businesses with different needs. A recent product, iMac, provides the Mac technology and interface in a low-cost package.

   While Mac users represent only about 5% of the total numbers of personal computer users, Macs are highly popular and almost a cultural necessity among graphic designers and online visual artists and the companies they work for. In general, Mac users tend to be enthusiasts.

   The MMX technology consists of three improvements over the non-MMX Pentium microprocessor:

1. 57 new microprocessor instructions have been added that are designed to handle video, audio, and graphical data more efficiently.
2. A new process, Single Instruction Multiple Data (SIMD), makes it possible for one instruction to perform the same operation on multiple data items.
3. The memory cache on the microprocessor has increased to 32 thousand bytes, meaning fewer accesses to memory that is off the microprocessor.

   In recent years, the 2400 bps modem that could carry e-mail has become obsolete. 14.4 Kbps and 28.8 Kbps modems were temporary landing places on the way to the much higher bandwidth devices and carriers of tomorrow. From early 1998, most new personal computers came with 56 Kbps modems. By comparison, using a digital ISDN adapter instead of a conventional modem, the same telephone wire can now carry up to 128 Kbps. With Digital Subscriber Line (DSL) systems, now being deployed in a number of communities, bandwidth on twisted-pair can be in the megabit range.

• The microprocessor
• (Optionally) coprocessors
• Memory
• BIOS
• Expansion slots
• Interconnecting circuitry

   Additional components can be added to a motherboard through its expansion slots. The electronic interface between the motherboard and the smaller boards or cards in the expansion slots is called the bus.

With the advent of parallel processing, multiprocessing is divided into symmetric multiprocessing (SMP) and massively parallel processing (MPP).

   In symmetric (or "tightly coupled") multiprocessing, the processors share memory and the I/O bus or data path. A single copy of the operating system is in charge of all the processors. SMP, also known as a "shared everything" system, does not usually exceed 16 processors.

   In massively parallel (or "loosely coupled") processing, up to 200 or more processors can work on the same application. Each processor has its own operating system and memory, but an "interconnect" arrangement of data paths allows messages to be sent between processors. Typically, the setup for MPP is more complicated, requiring thought about how to partition a common database among processors and how to assign work among the processors. An MPP system is also known as a "shared nothing" system.

   Multiprocessing should not be confused with multiprogramming, or the interleaved execution of two or more programs by a processor. Today, the term is rarely used since all but the most specialized computer operating systems support multiprogramming. Multiprocessing can also be confused with multitasking, the management of programs and the system services they request as tasks that can be interleaved, and with multithreading, the management of multiple execution paths through the computer or of multiple users sharing the same copy of a program.

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