1. 1 COMS 161 Introduction to Computing Title: Computing Basics Date: September 17, 2004 Lecture Number: 11

2. 2 Announcements

3. 3 Review Computer System Basics

4. 4 Outline Computer System Basics Connecting to the Digital Domain

5. 5 Without power everything in main memory is lost How does a computer start itself? Booting

6. 6 Special start-up instructions are stored in ROM –BIOS (basic input-output system) Booting

7. 7 BIOS loads the operating system from disk into main memory –After instructions are loaded into memory, the CPU executes them Booting

8. 8 How Much RAM? Your computer’s RAM is not its hard disk –RAM is main memory –Disk storage is secondary storage or mass storage –More on that later More RAM costs more money –More RAM does not make your computer faster –But it does let you do more stuff

9. 9 Bidirectional bus –Data flows to and from memory Into and out of memory Computer Systems

10. 10 Read memory (read from memory) –Memory controller access word at specified address for a read operation –Data in the memory is put on the data bus Write memory (write to memory) –Data to write into memory is on the data bus –Memory controller access word at specified address for a write operation Computer Systems

11. 11 Peripheral devices –Components added to the basic computer system –Increase the systems functionality –Secondary memory Hard disks CD/RW DVD/RW –Input/output devices Computer Systems

12. 12 Software Programs –Written using programming languages (symbolic codes for expressing computer instructions) Compiled into assembly code Assembled into machine code Linked with other machine code Loaded someone in memory –Usually sequential instruction execution

13. 13 Software Conditional processing –The ability to alternative actions based on the recognition of changing conditions 1011001010 0101100101 0100010011 1001001111 1110101001 1101001010 1010100101 0100011101 1110101001 0100010011 1110101001 0101100101 0100010011

14. 14 Conditional Processing Program execution depends on certain conditions If (ProfP) { Print(“A one of a kind”); Print(“Y’all gonna miss me”); } else { Print(“We are the happy idiots”); Print(“The mediocre”); Print(“Those who fear excellence”); }

15. 15 Operating Systems Collection of resident programs –Manage the computer’s resources –Supervise the execution of processes –Provide useful services and security Continuous control of system Supervises processes Creates useful abstractions for users Defines computing experience

16. 16 Managing Files File –sequence of items treated as a unit –identified with a unique name Filenames are composed of –identifier + ‘.’ + extension Identifier –(Windows) up to 255 symbols excluding special characters Extension –(Windows) 1 - 4 characters –used to classify file

17. 17 Hierarchical File System tree--special type of graph nodes, edges (links) parent(s) child(ren) ancestor(s) descendant(s) directory structure-- series of levels based on a tree files, folders path--list of all ancestors of a file/folder from root pathname-- conventional listing of path

18. 18 Windows Example