Computer instructions have exactly defined and limited vocabulary, syntax, and grammar {formal language, programming} {programming language}| {computer language}, with no ambiguities or connotations.
parts
Programming languages have alphabet {character set} that makes numbers and words in formats. They have mathematical functions, logical operations, and string manipulations {operator, programming}. They have processing instructions {executable}. They have sentences {declaration, programming} {non-executable declaration} that name, set up arrays, or create symbols.
levels
Machine uses machine-dependent binary code {machine language}. Assembler uses machine-dependent three-letter codes {assembly language} for instructions and addresses and has one statement for each instruction. People use higher-level languages {compiler language} {high-level language}, with one statement for several instructions, such as BASIC, FORTRAN, COBOL, UNIX, and DOS.
early procedural computer language {ALGOL language}.
Simple basic-function languages {BASIC language} can be for interactive use.
early procedural computer language {COBOL language}.
Computer languages {Java language} can be object oriented. Java has classes with methods. A main static method may be first. Methods use "get" and "put" for getting and setting values, "is" or "has" for boolean test functions, and action verbs for methods that change state or take action in other ways. Methods should proceed from public to protected to private. Within each group, methods should start with constructors, then instance methods, then static methods. Java has local and global class member instance variables and static member variables. Java has constants. Create output using System.out.println. The entire system has to be layered and buildable in a single pass. A script defines the order in which the packages are built. Java 2 Enterprise Edition (J2EE) defines application servers for Enterprise Java Beans (EJB), Servlets, and Java Server Pages (JSP), to make web-enabled applications.
Interactive computer languages {LISP language} can be for symbol manipulation. Symbols can be numbers, words {atom, LISP}, or groups {list, LISP}. Data and operations are both lists {list structure}. Programs use, modify, and recognize lists. List addresses contain two pointers, one to current list value and other to next list item. LISP can perform all string operations and compare lists and operations. Lists can have any number of dimensions.
Relational database queries use a language {SQL language} {Structured Query Language}. Make variable names no more than 31 characters. Declare cursors explicitly. Primary cursors remain open. Secondary cursors close after fetching all rows.
table
In a database, each data structure is a table, with columns and rows. The rows are records, a set of information about one item, and the columns are each attributes of the item.
datatype
Each column has entries all in one datatype. The datatypes are integer, floating point number, fixed length field of n characters, variable length field of characters, bit, binary fixed length field of n characters, money, and date and time. A "null" entry means an unknown entry, not blank or zero.
queries
select column, column, ... from table - retrieves data from columns in the table and displays in the order specified.
select column from table where phrase - phrase sets conditions for selection. The phrase may use symbols such as =, >, <, >=, <=, !=, !>, and !< and may use connectors such as and, or, not, between m and n, is null, is not null, in ( ... ), not in ( ... ), and LIKE ' '. The symbols that can be used in LIKE are % for any string of 0 or more characters, _ for anyone character, [ ] for any single character in a range or set, [^] for any single character not in a range or set.
function
select function from table - runs a function, such as "getdate ()".
order
select column from table order by column - sorts in ascending order.
select column from table order by column desc - sorts in descending order.
group
select column from table group by column, column, ... - makes nested groups.
select column from table group by column having phrase - phrase sets conditions for grouping.
operator
select operator(column) - operators check numbers of entries: count(column), max(column), min(column), sum(column), avg(column).
insert
insert table (column, column, ... ) (column-1-name datatype, ...) values ('x', 'y') - inserts rows into table at the columns specified using the values in order.
update
update table set column, column, ... from table where phrase - modifies one table by updating its rows.
delete
delete table from table where phrase - deletes rows from table.
Exception
EXCEPTION traps errors. Some named exceptions are ZERO_DIVIDE, NO_DATA_FOUND, TOO_MANY_ROWS, VALUE_ERROR, OTHERS (for all errors). For example, EXCEPTION WHEN ZERO_DIVIDE THEN RESULT1 = NULL;. It has no continue.
3-Computer Science-Software-Programming
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Description of Outline of Knowledge Database
Date Modified: 2022.0225