More on data storage and representation CSC 2001

Overview  Memory  Gates  Storage methods  Memory organization  Basic architecture  Long bit streams  Memory  Gates  Storage methods  Memory organization  Basic architecture  Long bit streams

Gates  … a device that produces the output of a Boolean operation when given the operation’s input values

AND, OR, XOR, & NOT gates

A simple flip-flop circuit

Setting the output of flip-flop

Storage techniques  core (direction of magnetic field)  capacitors (charged or discharged)  flash memory (trapped electrons in silicon dioxide) (full or empty)  core (direction of magnetic field)  capacitors (charged or discharged)  flash memory (trapped electrons in silicon dioxide) (full or empty)

Bits, bytes, and beyond 1 byte = 8 bits 1KB = 1024 (2 10 ) bytes 1MB = (2 20 ) bytes 1GB = (2 30 ) bytes

Anatomy of a byte high-order end low-order end most significant bitleast significant bit

Memory organization  memory cells  cells contain chunks of memory (often 1 byte)  have addresses (sequentially numbered)  information can span multiple cells  memory cells  cells contain chunks of memory (often 1 byte)  have addresses (sequentially numbered)  information can span multiple cells

Memory organization

ROM vs. RAM  Read Only Memory  Random Access Memory  Read Only Memory  Random Access Memory

Mass storage  Auxiliary storage devices  magnetic disks  hard drives, Zip disks  single vs. multiple disks  read/write head  tracks/cylinders/sectors  formatting  performance  seek time, latency, access time, transfer rate  Auxiliary storage devices  magnetic disks  hard drives, Zip disks  single vs. multiple disks  read/write head  tracks/cylinders/sectors  formatting  performance  seek time, latency, access time, transfer rate

Hard disks

More mass storage  Compact disks (CD-ROMs)  single spiral-shaped track  DVD-ROMs  multiple, semitransparent layers  Magnetic tape  high capacity, cheap, reliable  slow access time  Compact disks (CD-ROMs)  single spiral-shaped track  DVD-ROMs  multiple, semitransparent layers  Magnetic tape  high capacity, cheap, reliable  slow access time

File storage and retrieval  physical vs. logical records  knowing where to look  defragmentation  physical vs. logical records  knowing where to look  defragmentation

Basic architecture Input device Output device Auxiliary storage device Central Processing Unit Control Unit Arithmetic/logic unit Memory unit

Basic architecture Input device Output device Auxiliary storage device Central Processing Unit Control Unit Arithmetic/logic unit Memory unit Input device mouse, keyboard, modem

Basic architecture Input device Output device Auxiliary storage device Central Processing Unit Control Unit Arithmetic/logic unit Memory unit Output device screen, printer, modem

Basic architecture Input device Output device Auxiliary storage device Central Processing Unit Control Unit Arithmetic/logic unit Memory unit CPU Control Unit, ALU MHz (10 6 ), GHz (10 9 ) 32-bit, 64-bit

Basic architecture Input device Output device Auxiliary storage device Central Processing Unit Control Unit Arithmetic/logic unit Memory unit RAM bits, bytes (8 bits), MB (2 20 bytes), GB (2 30 bytes)

Basic architecture Input device Output device Auxiliary storage device Central Processing Unit Control Unit Arithmetic/logic unit Memory unit Aux storage unit MB, GB Zip disks, CD-ROM, DVD-ROM, tapes, hard drives

Basic architecture  We’ll return to this in chapter 2  For now, understand that the computer has to be able to store bits, that there are different kinds of memory, and different purposes for these different kinds of memory.  We’ll return to this in chapter 2  For now, understand that the computer has to be able to store bits, that there are different kinds of memory, and different purposes for these different kinds of memory.

Data representation  Translating data into bits  Characters and numbers  Large amount of data imply lots of bits.  Working with long strings of 0s and 1s quickly becomes cumbersome.  Translating data into bits  Characters and numbers  Large amount of data imply lots of bits.  Working with long strings of 0s and 1s quickly becomes cumbersome.

Dealing with long bit streams  Other (more concise) notation is useful  hexadecimal  base 16  need symbols for numbers (because = )  Other (more concise) notation is useful  hexadecimal  base 16  need symbols for numbers (because = )

Hexadecimal (0-7) base 2base 10base base 2base 10base

Hexadecimal (8-15) base 2base 10base A B C D E F base 2base 10base A B C D E F

binary hex conversion Think in groups of four bits (start from right) Pad with 0 on left if needed = = = = DB AF = = E7 = = Think in groups of four bits (start from right) Pad with 0 on left if needed = = = = DB AF = = E7 = =

practice problems A7D31C A7D31C