The cpu is the most important component in a computer

 The CPU is the most important component in a computer.
 In the earliest computers, CPUs were huge devices made
of electrical and mechanical components such as vacuum
tubes and switches.
 Today, CPUs are small chips known as microprocessors .

CPEN 21_Programming Logic and Design- Introduction to Computers and Logic
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3. Output - After data items have been processed, the resulting information
usually is sent to a printer, monitor, or some other output device so people
can view, interpret, and use the results.
II. STORAGE DEVICES
Main Memory
 Main memory is where the computer stores a program while the program
is running.
 Main memory is commonly known as random-access memory or RAM .
 RAM is usually volatile type of memory that is used only for temporary
storage while a program is running.
 When the computer is turned off, the contents of RAM are erased.
Secondary Storage Devices
 Secondary storage is a type of memory that can hold data for long
periods of time, even when there is no power to the computer.
 Programs are normally stored in secondary memory and loaded into
main memory as needed.
 The most common type of secondary storage device is the disk drive .
 A disk drive stores data by magnetically encoding it onto a circular disk.
 External disk drives can be used to create backup copies of important
data or to move data to another computer.
 A floppy disk drive records data onto a small floppy disk, which can be
removed from the drive.
 Floppy disks hold only a small amount of data, are slow to access data,
and are sometimes unreliable.
 USB drives are small devices that plug into the computer’s USB
(universal serial bus) port, and appear to the system as a disk drive.
 They store data in a special type of memory known as flash memory.
 USB drives, which are also known as memory sticks and flash drives,
are inexpensive, reliable, and small enough to be carried in your pocket.
 Optical devices such as the CD (compact disc) and the DVD (digital
versatile disc) are also popular for data storage.

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 CD and DVD drives use a laser to detect the pits on disc surface and
thus read the encoded data.
 Optical discs hold large amounts of data, and because recordable CD
and DVD drives are now commonplace, they are good mediums for
creating backup copies of data.
III. HOW THE COMPUTER STORE DATA
 All data that is stored in a computer is converted to sequences of 0s and
1s.
 A computer’s memory is divided into tiny storage locations known as
bytes.
 Each byte is divided into eight smaller storage locations known as bits.
 The term bit stands for binary digit.
A. Storing Numbers
 A bit that is turned off represents the number 0 and a bit that is turned
on represents the number 1.
 The position of each digit in a binary number has a value assigned to it.
B. Storing Characters
 Any piece of data that is stored in a computer’s memory must be stored
as a binary number that includes characters, such as letters and
punctuation marks.