PGI Fortran Reference manual - The Portland Group

Fortran Data Types2.6.1. Array Declaration ElementAn array declaration has the following form:name([lb:]ub[,[lb:]ub]...)where name is the symbolic name of the array, lb is the specification of the lower bound of thedimension and ub is the specification of the upper bound. The upper bound, ub must be greaterthan or equal to the lower bound lb. The values lb and ub may be negative. The bound lb istaken to be 1 if it is not specified. The difference (ub-lb+1) specifies the number of elements inthat dimension. The number of lb,ub pairs specifies the rank of the array. Assuming the array isof a data type that requires N bytes per element, the total amount of storage of the array is:N*(ub-lb+1)*(ub-lb+1)*...The dimension specifiers of an array subroutine argument may themselves be subroutinearguments or members of COMMON.2.6.2. Deferred Shape ArraysDeferred-shape arrays are those arrays whose shape can be changed by an executable statement.Deferred-shape arrays are declared with a rank, but with no bounds information. Theyassume their shape when either an ALLOCATE statement or a REDIMENSION statement isencountered.For example, the following statement declares a deferred shape REAL array A of rank two:REAL A(:, :)2.6.3. SubscriptsA subscript is used to specify an array element for access. An array name qualified by a subscriptlist has the following form:name(sub[,sub]...)where there must be one sub entry for each dimension in array name.Each sub must be an integer expression yielding a value which is within the range of the lowerand upper bounds. Arrays are stored as a linear sequence of values in memory and are held suchthat the first element is in the first store location and the last element is in the last store location.In a multi-dimensional array the first subscript varies more rapidly than the second, the secondmore rapidly than the third, and so on (column major order).2.6.4. Character SubstringA character substring is a contiguous portion of a character variable and is of type character.A character substring can be referenced, assigned values and named. It can take either of thefollowing forms:character_variable_name(x1:x2)character_array_name(subscripts)(x1:x2)where x1 and x2 are integers and x1 denotes the left-hand character position and x2 the righthandone. These are known as substring expressions. In substring expressions x1 must be bothPGI Fortran Reference Guide 26