Chapter 12 Variables and Operators Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Basic C Elements Variables • named, typed data items Operators • predefined actions performed on data items • combined with variables to form expressions, statements Rules and usage Implementation using LC-3 12­2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Data Types C has three basic data types int integer (at least 16 bits) double floating point (at least 32 bits) char character (at least 8 bits) Exact size can vary, depending on processor • int is supposed to be "natural" integer size; for LC-3, that`s 16 bits -- 32 bits for most modern processors 12­3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Variable Names Any combination of letters, numbers, and underscore (_) Case matters • "sum" is different than "Sum" Cannot begin with a number • usually, variables beginning with underscore are used only in special library routines Only first 31 characters are used 12­4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Examples Legal wordsPerSecond same identifier words_per_second _green aReally_longName_moreThan31chars aReally_longName_moreThan31characters Illegal 10sdigit ten`sdigit done? reserved keyword double 12­5 ... - tailieumienphi.vn