CSC 2400: Computer Systems. Key to Success

Transcription

1 CSC 2400: Computer Systems Week 1 Goals and Introduction Dr. Mirela Damian Key to Success q Start early to allow +me for debugging 1

2 Policy: Write your own code q Programming in an individual creative process much like composition. You must reach your own understanding of the problem and discover a path to its solution. During this time, discussions with friends are encouraged. However, when the time comes to write code that solves the problem, such discussions are no longer appropriate The program must be your own work Programming Environment Linux machines felix.csc.villanova.edu, helix.csc.villanova.edu Unix machines csgate.csc.villanova.edu, tanner.csc.villanova.edu NFS tanner csgate SSH Any lab, or your own PC/Mac/Linux Computer SSH SSH helix felix 2

3 What do Computers Do? q Do a survey on campus Numerous correct answers Computers Execute Instruc+ons. That s all! What Kind of Instruc=ons? Strictly speaking, computers only understand machine language (binary machine code) Data plus Instructions 3

4 Compilation Stages count = 0; while (n > 1) { count++; if (n & 1) n = n*3 + 1; else n = n/2; } High level language mov ECX, 0.loop: cmp EDX, 1 jle.endloop add ECX, 1 mov EAX, EDX and EAX, 1 je.else mov EAX, EDX add EDX, EAX add EDX, EAX add EDX, 1 jmp.endif.else: sar EDX, 1.endif: jmp.loop.endloop: Assembly language Machine language To build an executable Building and Running $ gcc program.c o xprogram Result! Complete executable binary file! Machine language To run: $./xprogram 4

5 Understanding Compilers q You ve got to know assembly q Chances are, you ll never write in assembly - Compilers are much better & more patient than we are q Understanding assembly is key to machine-level execution model - Behavior of programs in presence of bugs - Tuning program performance Computer System q A computer system consists of hardware and systems software that cooperate to run application programs. q Computer systems hardware is comprised of 5 basic elements, as described by the Von Neumann architecture model (1945): CPU 5

6 Main Memory q Any program executing must be in memory q Main memory is an array of bytes or words: Memory Memory Addresses Central Processing Unit (CPU) CPU Control Unit ALU Addresses Data Instructions Memory A A A 000B 000C 000D 000E 000F FE10 FACE CAFE ACED CEDE Registers ABC DEF F00D EEEE 1111 EEEE B1B2 F1F q q q Control unit - Controls the operations of the computer - Fetches instructions, interprets them, and tells the ALU what to do Arithmetic and Logic Unit (ALU) - Executes low-level operations (+, -, *, /, etc.) Registers - High-speed temporary storage 6

7 A Typical Computer System One or more CPUs Device controllers connect through common bus Shared access to main memory Managing all these components requires a layer of software: the operating system Operating System Run Things Web Browser Music Player System Calls Users and User Programs Operating System CPU & Memory I/O Devices Hardware 7

8 Operating System q Users and programs can t directly access the hardware - OS provides a simpler, more powerful interface - OS services are higher level and can be accessed via system calls q Programs view the operating system as a set of System Calls (APIs) Course Goals q Goal 1: Programming in the large - Help you learn what you need to know to write efficient computer programs q Goal 2: Look under the hood High-level language (C) assembly language machine language (IA-32) 8

9 Course Feature: C q Q: Why C instead of Java? q A: C supports Goal 1 beuer - C is a lower- level language ü C provides more opportuni+es to create abstrac+ons q A: C supports Goal 2 beuer - C facilitates the language levels tour (closer to assembly) - C facilitates the service levels tour ü Linux is wriuen in C Course Feature: Linux q Q: Why Linux instead of MicrosoX Windows? q A: Linux is good for educa+on and research - Linux is open- source and well- specified q A: Linux is good for programming - Linux is a variant of Unix - Unix has GNU, a rich open- source programming environment Linux == Unix for our purposes 9

10 q Help you to become a... Course Goals: Summary Power Programmer!!! GeBng Started q Check out course web site now hup:// q Subscribe to the zybook Programming in C - Instruc+ons in the syllabus and the first assignment q First assignment posted online 10