lect01 - 9/3/11% CMSC 216 Introduction to Computer Systems...

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9/3/11 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://www.cs.umd.edu/class/ • If you don’t 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 (some Mondays as announced)! • Note: No Lab on Labor Day - Monday • TA office hours will start next Tuesday • Read Chapter 1 of Bryant and O’Hallaron, and Chapter 1 of Reek CMSC 216 - Wood, Sussman, Herman, Plane 2
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9/3/11 2 Introduction to Computer Systems • Course objectives • Expectations • Course policies • Discussion sections • Course projects • Submit server • Grades server 3 CMSC 216 - Wood, Sussman, Herman, Plane A T OUR OF C OMPUTER S YSTEMS Chapter 1, Bryant and O'Hallaron 4 CMSC 216 - Wood, Sussman, Herman, Plane
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9/3/11 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, Plane 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, Plane
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9/3/11 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, Plane 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, Plane
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9/3/11 5 Caching is important • Executing a program can mean reading instructions from disk into memory, then moving around data from memory to registers or memory to disk • Because some devices are much slower (maybe because they’re bigger), we can utilize caches to
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This note was uploaded on 01/13/2012 for the course CMSC 216 taught by Professor Plane during the Spring '11 term at Maryland.

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lect01 - 9/3/11% CMSC 216 Introduction to Computer Systems...

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