Information Manipulation CSCI-N 100 Dept. of Computer and Information Science

Doing what its told Computers deterministically perform instructions to process information Deterministically Computer determines which instruction to execute next Required by construction to execute a specific instruction based only on program and data given to it No alternatives, no options Will execute one and only one next instruction

Computers… Have no imagination or creativity Have no intuition Are literal (no decorum, irony, subtlety…) Do no have a sense of humor Are not vindictive, cruel… Are not purposeful Have no free will

The Process Information Manipulation Sits in switches called memory Memory just ‘holds’ information until called Cannot manipulate information in memory Manipulation Information called Placed in register Information manipulated Put back into memory

Fetch and Execute Cycle A sequence of actions Getting instructions Figuring out what to do Gather data needed to do it Doing it Saving the results Repeat (if necessary)… Happens millions of times, short period of time

What’s in the cycle Elemental commands (sometimes called machine language) Each computer has limited number How many not important Structures that process the information

The Structures Structures that process information Sequence – done in order one step after another Decision – yes/no, true/false Iteration – also called looping Computer will only follow directions given to it in the written program

What’s in the cycle (cont’d) Any change or interference in instructions can change computers ability to complete task and give any type of result Blue screen of death Cyclic redundancy Computer ‘froze’

Properties of memory Discrete locations Addresses Value Organized in order Addresses Location in memory with a given number Starts at zero (0) Value Contents of location Finite capacity Each location has capacity of 1 byte (8 bits)

Make it Stop Early computers had Start/Stop buttons Newer machines execute an “idle loop” Instructions continually check if there is anything to do Mouse click Keystroke