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records and structures
summary
This subchapter looks at records and structures.
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This subchapter looks at records and structures.
free computer programming text book projecttable of contents
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This subchapter is a stub section. It will be filled in with instructional material later. For now it serves the purpose of a place holder for the order of instruction.
Professors are invited to give feedback on both the proposed contents and the propsed order of this text book. Send commentary to Milo, PO Box 1361, Tustin, California, 92781, USA.
This subchapter looks at records and structures.
The word structure is used in most modern programming languages, while the word record is used in most early programming languages. They are the same programming concept.
A record or structure is a method of grouping several data items together. It is possible to manipulate and change individual data items in a record or structure and possible to manipulate the entire structure or record as a whole.
The individual items in a structure or record are typically called elelements.
Usually any operation that can be performed on a particular data type can be performed on an element that has that data type.
Common operations allowed on an entire record or structure include copying and printing.
Stanford CS Education Library This [the following section until marked as end of Stanford University items] is document #101, Essential C, in the Stanford CS Education Library. This and other educational materials are available for free at http://cslibrary.stanford.edu/. This article is free to be used, reproduced, excerpted, retransmitted, or sold so long as this notice is clearly reproduced at its beginning. Copyright 1996-2003, Nick Parlante, nick.parlante@cs.stanford.edu.
C has the usual facilities for grouping things together to form composite types-- arrays and records (which are called “structures”). The following definition declares a type called “struct fraction” that has two integer sub fields named “numerator” and “denominator”. If you forget the semicolon it tends to produce a syntax error in whatever thing follows the struct declaration.
struct fraction {
int numerator;
int denominator;
}; // Don't forget the semicolon!
This declaration introduces the type struct fraction (both words are required) as a new type. C uses the period (.) to access the fields in a record. You can copy two records of the same type using a single assignment statement, however == does not work on structs.
struct fraction f1, f2; // declare two fractions
f1.numerator = 22;
f1.denominator = 7;
f2 = f1; // this copies over the whole struct
Stanford CS Education Library This [the above section] is document #101, Essential C, in the Stanford CS Education Library. This and other educational materials are available for free at http://cslibrary.stanford.edu/. This article is free to be used, reproduced, excerpted, retransmitted, or sold so long as this notice is clearly reproduced at its beginning. Copyright 1996-2003, Nick Parlante, nick.parlante@cs.stanford.edu.
“31 Every object in the language has a type, which characterizes a set of values and a set of applicable operations. The main classes of types are elementary types (comprising enumeration, numeric, and access types) and composite types (including array and record types).” —:Ada-Europe’s Ada Reference Manual: Introduction: Language Summary See legal information
“34/2 Composite types allow definitions of structured objects with related components. The composite types in the language include arrays and records. … A record is an object with named components of possibly different types.” —:Ada-Europe’s Ada Reference Manual: Introduction: Language Summary See legal information
“35 Record, task, and protected types may have special components called discriminants which parameterize the type. Variant record structures that depend on the values of discriminants can be defined within a record type.” —:Ada-Europe’s Ada Reference Manual: Introduction: Language Summary See legal information
The following material is from the unclassified Computer Programming Manual for the JOVIAL (J73) Language, RADC-TR-81-143, Final Technical Report of June 1981.
Chapter 1 INTRODUCTION, page 3
Items are just the scalar (single-value) data of JOVIAL. JOVIAL
also has tables and blocks, which provide for arrays and other
data structures.
An example of a table declaration is:
TABLE GRID (1:10, 1:10);
BEGIN
ITEM XOORD U;
ITEM YCOORD U;
END
The table GRID has two dimensions. Each dimension contains ten
entries. Each entry consists of two items, XCOORD and YCOORD.
Chapter 1 INTRODUCTION, page 5
“18. A program without a loop and a structured variable isn’t worth writing.” —Alan Perlis, Epigrams on Programming, ACM’s SIGPLAN Notices Volume 17, No. 9, September 1982, pages 7-13
Coding example: I am making heavily documented and explained open source code for a method to play music for free — almost any song, no subscription fees, no download costs, no advertisements, all completely legal. This is done by building a front-end to YouTube (which checks the copyright permissions for you).
View music player in action: www.musicinpublic.com/.
Create your own copy from the original source code/ (presented for learning programming).
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