Computer Programming I. Today’s Lecture Components of a computer Program Programming language ...
-
Upload
kerry-warren -
Category
Documents
-
view
237 -
download
3
Transcript of Computer Programming I. Today’s Lecture Components of a computer Program Programming language ...
Copyright © 2006 Pearson Addison-Wesley. All rights reserved. 1-3
Computer Components
HardwareCPU IO deviceMain memory
Software How does computer work?
Memory
Random Access Memory (RAM)Temporary memoryMain memory
Read Only Memory (ROM)For start-up directionspermanent memory.
Programs
Computer Hardware Software
Programs that run on a computerOperating systemApplication software
Copyright © 2006 Pearson Addison-Wesley. All rights reserved. 1-9
Programming Languages
Three types of programming languages
1. Machine languages Strings of numbers giving machine
specific instructions Example:
+1300042774
+1400593419
+1200274027
Copyright © 2006 Pearson Addison-Wesley. All rights reserved. 1-10
Programming Languages
Three types of programming languages
2. Assembly languages English-like abbreviations representing
elementary computer operations (translated via assemblers)
Example:LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY
Copyright © 2006 Pearson Addison-Wesley. All rights reserved. 1-11
Programming Languages
Three types of programming languages
3. High-level languages Codes similar to everyday English Use mathematical notations (translated via
compilers) Example:
grossPay = basePay + overTimePay
Copyright © 2006 Pearson Addison-Wesley. All rights reserved. 1-12
Programming Languages (3)
Machine Languages
Assembly Languages
High-Level Languages
+1300042774+1400593419+1200274027
LOAD AADD B
STORE C
C=A+B
Copyright © 2006 Pearson Addison-Wesley. All rights reserved. 1-13
C++
C++ is a third generation language Why C++ not C
C++ is an object oriented language
Decimal System
Positional base 10 numeral systems 10 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 Use same symbol for different orders of
magnitude For example, “1262” in base 10
1*103+2*102+6*101+2*100
Binary
A computer is a “bistable” device A bistable device:
Easy to design and build Has 2 states: 0 and 1
One Binary digit (bit) represents 2 possible states (0, 1)
Decimal to Binary representation 0: 0 1: 1 2: 10
3: 11 4: 100
5: 101 6: 110 7: 111 8: 1000
9: 1001
10: 1010 11: 1011 12: 1100
13: 1101 14: 1110 15: 1111 16: 10000 17: 10001
Convert Binary to Decimal
18
Interpret binary numbers (transform to base 10) 1101
= 1*23+1*22+0*21+1*20=8+4+0+1=13 Translate the following binary number to
decimal number 101011
Convert Decimal to Binary
Procedure:
1. Divide the decimal number by 2
2. Make the remainder the next digit to the left of the answer
3. Replace the decimal number with the quotient
4. If quotient is not zero, Repeat 1-4; otherwise, done
Algorithm
A finite set of well-defined instructions for accomplishing some task which, given an initial state, will terminate in a corresponding recognizable end-state.
Examples: Select the largest number from a set of number (n)
Suppose n numbers are a1, a2, …an Set LG=a1; For i=2 to n, do
if LG<ai, then set LG=ai; Else do nothing;
The largest number is LG
Convert Decimal number 100 to Binary Number
100 % 2 = 0=> last digit100 / 2 = 5050 % 2 = 0 => 2nd last digit50/2 = 2525 % 2 = 1 => 3rd last digit25 / 2 = 1212 % 2 = 0 => 4th last digit
12 / 2 = 66 % 2 = 0 => 5th last digit6 / 2 = 3 3 % 2 = 1 => 6th last digit3 / 2 =1 1 % 2 = 1 => 7th last digit1 / 2 = 0
The result is 1100100
Bytes and Words A group of 8 bits is a byte A byte can represent 28 = 256 possible
states Several bytes grouped together to form a
word Word length of a computer, e.g., 32 bits
computer, 64 bits computer
Representing Text Text is a series of characters
letters, punctuation marks, digits 0, 1, …9, spaces, return (change a line),…
How many bits do we need to represent a character? 1 bit can be used to represent 2 different things 2 bit … 2*2 = 22 different
things n bit 2n different things
In order to represent 128 different character Solve 2n = 128 for n n=7
ASCII The American Standard Code for Information
Interchange 128 characters 7 bits could be used to represent ASCII
characters However, in 1960s, an 8-bit byte was
becoming hardware standard, therefore, it was decided to use 1 byte (8 bits) to store the ASCII code (first 7 bits), with the eighth bit being used as a parity bit to detect transmission errors