A digital computer is a fast electronic calculating machine that accepts digitized input information, processes it according to a list of internally stored instructions, and produces the resulting output information.
? The list of instructions is called a computer program, and the internal storage is called computer memory.
? Types of Computers
1. Personal Computers. This is the most common computer which has found wide use in homes, schools, and business offices.
2. Workstations. Although still of desktop dimensions, these machines have a computational power which is significantly higher than that of personal computers. Workstations are often used in ...view middle of the document...
Typical word lengths range from 16 to 64 bits. The MM is organized so that the contents of one word, containing n bits, can be stored or retrieved in one basic operation.
Since programs must reside in MM during execution, MM is often referred to as the bottleneck in most computer operations.
To provide easy access to any word in MM, a distinct address is associated with each word location. Addresses are numbers that identify successive locations.
MM is also known as random-access memory (RAM). RAM is memory in which any location can be reached in a short, fixed amount of time.
The time required to access one word is the memory access time. For RAMs, this time is fixed, independent of the location of the word being accesses. It typically ranges from 10 to 100 nanoseconds for most modern computers.
2. Secondary Storage. This is used when large amounts of data have to be stored, particularly if some of the data need not be accessed very frequently.
Examples: magnetic disks, drums, tapes
? Arithmetic and Logic Unit (ALU). This is where the execution of most operations takes place. It contains a number of high-speed storage elements called registers.
used for temporary storage of frequently used operands.
Each register can store one word of data.