A digital computer is a collection of logic elements that can execute arbitrary algorithms to perform data calculation and manipulation functions. A computer is composed of a microprocessor, memory, and some input/output (I/O) elements as shown in Fig. 3.1. The microprocessor, often called a microprocessor unit (MPU) or central processing unit (CPU), contains logic to step through an algorithm, called a program , that has been stored in the computer’s program memory. The data used and manipulated by that program is held in the computer’s data memory. Memory is a repository for data that is usually organized as a linear array of individually accessible locations. The microprocessor can access a particular location in memory by presenting a memory address (the index of the desired location) to the memory element. I/O elements enable the microprocessor to communicate with the outside world to acquire new data and present the results of its programmed computations.
Such elements can include a keyboard or display controller. Programs are composed of many very simple individual operations, called instructions, that specify in exact detail how the microprocessor should carry out an algorithm. A simple program may have dozens of instructions, whereas a complex program can have tens of millions of instructions.
Collectively, the programs that run on microprocessors are called software
, in contrast to the hardware on which they run. Each type of microprocessor has its own
instruction set that defines the full set of unique, discrete operations that it is capable of executing. These instructions perform very narrow tasks that, on their own, may seem insignificant. However, when thousands or millions of these tiny instructions are strung together, they may create a video game or a word processor.
A microprocessor possesses no inherent intelligence or capability to spontaneously begin performing useful work. Each microprocessor is constructed with an instruction set that can be invoked in arbitrary sequences. Therefore, a microprocessor has the potential to perform useful work but will do nothing of the sort on its own. To make the microprocessor perform useful work, it requires explicit guidance in the form of software programming. A task of even moderate complexity must be broken down into many tiny steps to be implemented on a microprocessor. These steps include basic arithmetic, Boolean operations, loading data from memory or an input element such as a keyboard, and storing data back to memory or an output element such as a printer. Memory structure is one of a computer’s key characteristics, because the microprocessor is almost constantly accessing it to retrieve a new instruction, load new data to operate on, or store a calculated result. While program and data memory are logically distinct classifications, they may share the same physical memory resource.
Random access memory (RAM) is the term used to describe a generic memory resource whose locations can be accessed, or addressed , in an arbitrary order and either read or written. A read
is the process of retrieving data from a memory address and loading it into the microprocessor. A write is the process of storing data to a memory address from the microprocessor. Both programs and data can occupy RAM. Consider your desktop computer.
Such elements can include a keyboard or display controller. Programs are composed of many very simple individual operations, called instructions, that specify in exact detail how the microprocessor should carry out an algorithm. A simple program may have dozens of instructions, whereas a complex program can have tens of millions of instructions.
Collectively, the programs that run on microprocessors are called software
, in contrast to the hardware on which they run. Each type of microprocessor has its own
instruction set that defines the full set of unique, discrete operations that it is capable of executing. These instructions perform very narrow tasks that, on their own, may seem insignificant. However, when thousands or millions of these tiny instructions are strung together, they may create a video game or a word processor.
A microprocessor possesses no inherent intelligence or capability to spontaneously begin performing useful work. Each microprocessor is constructed with an instruction set that can be invoked in arbitrary sequences. Therefore, a microprocessor has the potential to perform useful work but will do nothing of the sort on its own. To make the microprocessor perform useful work, it requires explicit guidance in the form of software programming. A task of even moderate complexity must be broken down into many tiny steps to be implemented on a microprocessor. These steps include basic arithmetic, Boolean operations, loading data from memory or an input element such as a keyboard, and storing data back to memory or an output element such as a printer. Memory structure is one of a computer’s key characteristics, because the microprocessor is almost constantly accessing it to retrieve a new instruction, load new data to operate on, or store a calculated result. While program and data memory are logically distinct classifications, they may share the same physical memory resource.
Random access memory (RAM) is the term used to describe a generic memory resource whose locations can be accessed, or addressed , in an arbitrary order and either read or written. A read
is the process of retrieving data from a memory address and loading it into the microprocessor. A write is the process of storing data to a memory address from the microprocessor. Both programs and data can occupy RAM. Consider your desktop computer.
