Using Pointers, Arrays, and Structs in Programming

Pointer Arrays & Structs ENEE150 0102 ANDREW GOFFIN

Project 2 Questions? Make sure you know what you re passing into printf/scanf: scanf can only take addresses/pointers printf takes values , except with pointer and strings, where it takes pointers Goffin ENEE150

Pointer Arrays An array of pointers Can be denoted with double pointer char **argv == char *argv[] Can be dereferenced twice! Once to get a pointer value, and again to get the value stored at said pointer Most obvious application is command line arguments Goffin ENEE150

Structures Compound datatypes Datatypes made up of primitive datatypes (int, char, float, etc.) Similar to arrays: Primitive data grouped together Can group data of different types! Useful for convenience and clarity of code Goffin ENEE150

Declaring Structs struct example{ int ex1; char ex2; float ex3[10]; }; struct example var; var.ex1 = 0; var.ex2 = c ; // determine fields in struct in this declaration // fields can be of ANY datatype (including datatype of struct!) // access fields with . operator // the datatype is called struct example Goffin ENEE150

Different ways to define structs /*define variable var from get-go */ struct example { } var; // easier declaration typedef struct example { } newtype, *ptype; newtype var; ptype pvar; // pointer to newtype Goffin ENEE150

Various Struct Notes Comparing structs? Cannot do struct1 == struct 2 Must compare field-by-field Setting structs? CAN do struct1 = struct2 Does a field-by-field copy Goffin ENEE150

Pointers to Structs Declare much like pointers to other datatypes Pointer points to first element in struct Accessing elements: (*pstruct).field accesses field Can be streamlined with the -> operator (*pstruct).field == pstruct->field Goffin ENEE150

Structs and Functions Again, treat like other datatypes Structs can be used as parameters or return types struct example foo(struct example var); Takes struct as parameter and returns the same struct from the function Goffin ENEE150