David Stotts Computer Science Department UNC Chapel Hill

0. data (types, simple information) 1. data storage (variables, assignment) 2. data retrieval (expressions, evaluation) 3. repetition (loops) 4. decision making (conditionals) 5. procedure abstraction (functions) 6. data abstraction (arrays) 7. objects: all-the-above, wrapped up

 We can’t study data storage and retrieval without knowing what “data” is Data the basic symbols and information that a computer manipulates  Data is why we write programs in the first place… we have questions, we want answers  Want information we have (input) turned into new information we need (output)

Input information we have and want a program to work on… we have to get it from the user and make it available to the program, in the computer memory Output the new info we expect the program to produce, to generate, to compute… we have to get it out of the program and back to the user in a form the user can consume and employ I/O is the term we use

computer I/O Cloud, etc.

Number 4, 10, -23, , -414, , , 7.0, e e integers and reals

String “tarheels” “x” “ ” “(919) ” aol.com” “hola ! !” “$ntko # &”

Boolean  true, false (yes, no) are the only values  the basis for “logic”

Number + - / * % 4+5   * 7  – 1.1  2.3 7/2  % 12  5 “mod”

Text + concat substring “abc” + “123”  “abc123” we call this concatenation “abc”.concat(“123”)  “abc123” “tarheels”.substring(3)  “heels” “tarheels”.substring(0,2)  “tar”

Boolean && || ! true && true  true AND true && false  false false && false  false true || false  true OR true || true  true false || false  false !false  true NOT !true  false

Comparisons 5 < 8  true less than 17 <= 3.28  false less than or equal 21.4 > -34  true greater than 1.0 >= 1.1  false greater than or equal 12.3 == 2.8  false equal to 12.3 === 2.8  false equal to (safe) -3 != -3.1  true not equal to -3 !== -3.1  true not equal to (safe)

Comparisons work on strings too “hello” < “world”  true alpha order-ish “bigfoot” > “big”  true “tar” == “tarheels”  false “tar” < “tarheels”  true (it’s shorter) “Upper” != “upper”  true case matters “upper” > “Upper”  true (seems strange) “5” > “4”  true these are not numbers “5” > “40”  true remember… alpha order