History of Computers

1
History of Computers

• Types of computers
• Mechanical
• Early electronic
• Mainframes
• Minicomputers
• Microcomputers
• Personal computers
• Laptop computers

2
Computer Architecture

• Inside a computer
• CPU
• Central Processing Unit
• Memory
• Instruction/data bus
• Input devices
• Keyboard, card reader
• Output devices
• Monitor, printer
• Storage devices
• Disk, CD/ROM, Flash drive

3
Programming Languages

• Growth of programming languages
• Machine code
• Octal or hex codes corresponding to the bit
  pattern for each instruction
• Assembly language
• Mnemonics for each code, names for memory
  locations
• Early languages and structured programming
• BASIC, COBOL, FORTRAN, PL/1
• Variables, operations, flow of control
• Modern object-oriented languages
• Ada, C, Java
• Objects with attributes (data) and methods
  (operations)

4
Data Storage

• Storage Units
• Bits (binary digits), bytes (8 bits), words (2,
  4, or 8 bytes)
• Data Representation
• Decimal Base 10, the numbers used by modern
  humans
• Binary Base 2, only uses digits 0 and 1
• Each bit position is a power of 2 (010011012
  64841 77)
• Octal Base 8, uses digits 0-7, coded as groups
  of 3 bits
• Each bit position is a power of 8 (1158 6485
  77)
• Hexadecimal Base 16, uses 0-9 and A-F, groups
  of 4 bits
• Each bit position is a power of 16 (4D16 6413
  77)

5
C Data Types

• Integer data
• Integer values can be stored in a byte, word, or
  long word
• In C the values can be signed or unsigned
• Negative numbers are stored in twos-complement
  form
• To get a negative integer, invert each bit of the
  positive value and add one
• Character data
• C uses the ASCII character set
• The character 0 is stored in memory as 30 hex,
  or decimal 48
• Floating point data
• C uses two sizes depending on precision
  required
• float 4 bytes, range 10-38 to 1038 ,
  accurate to 7 places
• double 8 bytes, range 10-308 to 10308, accurate
  to 15 places

6
C Control Structures

• Arithmetic
• Standard arithmetic operations
• , , , /, and (mod)
• Sequential
• A series of statements executed in order
• Conditional
• Decide what to do based on data in the program
• Looping
• Repeat processing based on some loop condition

while (condition) sequence_of_statements
do sequence_of_statements while
(condition) for (initialize condition
increment) statements_to_repeat
if (condition) sequence_of_statements else
some_other_statements
int myNumber 1 myNumber myNumber
myNumber 4