Data Types in C: Understanding Variables and Operations, Slides of Computer Science

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Data Types in C

Data Transformation

• Programs transform data from one form to another
  • Input data  Output data
  • Stimulus  Response
• Programming languages store and process data in various ways depending on the type of the data; consequently, all data read, processed, or written by a program must have a type
• Two distinguishing characteristics of a programming language are the data types it supports and the operations on those data types

A Data Type (continued)

• When the compiler encounters a declaration for a

variable, it sets up a memory location for it

• An operator used on a variable or variables is legal

only if

• The operator is defined in that programming language for a variable of that type
• The variable or variables involved with the operator are of the same or compatible types

Rules for Constructing Identifiers in C

• Capital letters A-Z, lowercase letters a-z, digits 0- 9, and the underscore character
• First character must be a letter or underscore
• Usually only the first 32 characters are significant
• There can be no embedded blanks
• Keywords cannot be used as identifiers
• Identifiers are case sensitive

Identifiers refer to the names of data types, constants, variables, and functions

Fundamental Data Types

• void – used to denote the type with no values
• int – used to denote an integer type
• char – used to denote a character type
• float, double – used to denote a floating

point type

• int *, float *, char * – used to denote a

pointer type, which is a memory address type

Uses of Fundamental Data Types

int elevationIndicator; char inputSymbol; float totalCost;

int main (void) { double grossProduct; int *temperatureValuePtr;

grossProduct = 4567.89; inputSymbol = 'a';

return (0); } // End main

Uses of Derived Data Types

int elevationTable[20];

char inputSymbols[] = "Hello World";

struct operationsStruct { double heatReading; int temperatureValue; float speedMeter; char actionCode; }; // End struct

struct operationsStruct currentOperations;

Records (Structures)

• A record permits a programmer to handle a group of variables as one variable
• The fields (members) of a record can be any built- in or programmer-defined data type
• A record can have values assigned to and read from it just like the built-in variable types
• A record can also be passed as an argument to a function and serve as the return value for a function

Basic Operations on Records

currentOperations.speedMeter = 245.6; currentOperations.temperatureValue = 67; currentOperations.actionCode = 'z';

latestReading = currentOperations.heatReading;

statusFactor = currentOperations.speedMeter * currentOperations.temperatureValue;

futureOperations = currentOperations;

printf("Temp: %d Code: %c\n", futureOperations.temperatureValue, futureOperations.actionCode);

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