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Machine Architecture. An Introduction to Computer Components. Major Computer Components. Central Processing Unit (CPU) Bus Main Memory (RAM) Secondary Storage I / O Devices Starting the computer. CPU. Central Processing Unit The Brain Controls all other computer functions. The Bus.
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Machine Architecture An Introduction to Computer Components
Major Computer Components • Central Processing Unit (CPU) • Bus • Main Memory (RAM) • Secondary Storage • I / O Devices • Starting the computer
CPU • Central Processing Unit • The Brain • Controls all other computer functions
The Bus • Computer components are connected by a bus • A bus is a group of parallel wires that carry control signals and data between components
Main Memory • Main memory is made up of capacitors • If the capacitor is charged, then its state is said to be 1 or ON. • We could also say the the bit is set. • If the capacitor does not have a charge, then its state is 0 or OFF. • We could also say that the bit is reset or cleared.
Size of Capacitors • Has decreased dramatically over the last 20 years. • Now we can fit several million capacitors on a chip the size of a dime. • As this technology becomes older, we can expect the price of memory to decrease. Is it already decreasing ? ABSOLUTELY !
Memory, the continuing saga • Memory is divided into cells, where each cell contains 8 bits. Remember that 8 bits is called a byte. • Each of these cells is numbered. • The number associated with a cell is known as its address. • Volatile storage
Reading & Writing • In addition to the circuitry that holds the bits, there are other circuits that allow other components to • Get the value of the data held at a particular address - known as a READ. • OR store data at that address - known as a WRITE.
Memory Access • All addresses in memory can be accessed in the same amount of time. • We DO NOT have to start at address 0 and read everything until we get to the address we really want. • We can go directly to the address we want and access the data. • That is why we call Main Memory RAM - Random Access Memory
Secondary Storage • Disks -- floppy, hard, removable • Tapes (sequential access) • CDs • Stores files • programs • data files (binary, text) • directory structure • Persistent storage
I/O • I/O is handled by peripheral devices. • A peripheral device is some machine that is not an integral part of the computer. • Examples: • monitor • keyboard • mouse • disk drive • printer • scanner
Media • Many I/O devices work in conjunction with media • A medium holds information (programs, data, text files) • Examples: • floppy disk (not the drive itself) • hard disk (not the drive itself) • magnetic tape (not the drive itself)
Bits, Bytes, and Words • A byte is 8 bits • A word is 32 bits or 4 bytes • Long word = 8 bytes = 64 bits • Quad word = 16 bytes = 128 bits • Programming languages use these standard number of bits when organizing data storage and access. • What do you call 4 bits ?? (hint: it is a small byte)
Booting the Computer • The term boot comes from the expression pulling yourself up by your bootstraps. • It refers to the computer’s start-up procedure. • When the computer is first turned on, it reads start-up instructions found in the ROM chips.
Booting the Computer (continued) • These instructions cause the computer to do a series of tests. Each of the components is tested. • The last thing that happens during boot is that the operating system is loaded from the hard disk into RAM. • The computer cannot do anything until the operating system is loaded, because the operating system manages all of the basic functions of the computer.
