1 Introduction

1 Introduction - 1/26/11 1 CMSC 216 Introduction to...

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Unformatted text preview: 1/26/11 1 CMSC 216 Introduction to Computer Systems Lecture 1 Introduction Jan Plane & Pete Keleher {jplane, keleher}@cs.umd.edu Administrivia Course home page is at http://lagoon.cs.umd.edu/216 If you dont already have a GLUE account, request one at http://www.oit.umd.edu/new/ Bring your laptop to discussion section on the next two Wednesdays and - after that Every Wednesday! Read Chapter 1 of Bryant and OHallaron, and Chapter 1 of Reek CMSC 216 - Wood, Sussman, Herman 2 1/26/11 2 Introduction to Computer Systems Course objectives Expectations Course policies Discussion sections Course projects Submit server Grades server 3 CMSC 216 - Wood, Sussman, Herman A TOUR OF COMPUTER SYSTEMS Chapter 1, Bryant and O'Hallaron 4 CMSC 216 - Wood, Sussman, Herman 1/26/11 3 Storage of Information Computers store all data as binary digits, or bits; groups of 8 bits are often called bytes How these bits are treated depends on their context the same sequence of bits can be used to represent a character, or an integer, or a floating- point number, or an instruction, or... it's all a matter of interpretation 5 CMSC 216 - Wood, Sussman, Herman Instruction-based execution Each program on a computer is a sequence of instructions written in machine language Processor executes one instruction at a time in a program, then executes the next one in turn To study code in this form, it's helpful to use assembly language rather than machine language code 6 CMSC 216 - Wood, Sussman, Herman 1/26/11 4 Example assembly program main: mov #0,sum ; set sum to 0 mov #1,num ; set num to 1 loop: add num,sum ; add num to sum add #1,num ; add 1 to num ble num,#1000,loop ; if num <= 1000, go back to 'loop halt ; end of program. stop running This is a slightly modified version of the example in Wikipedia's Computer article What does this program do? Sequence of operations doesn't always go to the next instruction in memory 7 CMSC 216 - Wood, Sussman, Herman Computer layout Lots of places to store information: CPU registers CPU caches Main memory Hard drives Remote storage The farther away from the CPU you go, the longer it takes to access data Typical programs have to access data stored on a hard drive, which is quite slow compared to other storage mediums 8 CMSC 216 - Wood, Sussman, Herman 1/26/11...
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1 Introduction - 1/26/11 1 CMSC 216 Introduction to...

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