FORNEXT

FORNEXT is a term used to describe the counting loop construct found in many BASIC-derived programming languages. It pairs a FOR statement that initializes a loop counter with a NEXT statement that advances the counter and marks the end of the loop. The overall effect is to repeat a block of code a specified number of times, with control determined by a start value, an end value, and an optional step value.

Syntax and dialects vary, but the general pattern is familiar. In classic BASIC, the loop looks like: FOR variable = start TO end [STEP step] … NEXT variable. In Visual Basic and some modern variants, the form is For variable = start To end [Step step] … Next variable. Some dialects allow NEXT without repeating the variable, while others require the matching counter name. If STEP is omitted, a default of 1 is usually assumed.

Behavior and usage notes. The loop executes the body, then the counter is incremented by STEP. If STEP is positive, the loop ends when the counter exceeds the end value; if STEP is negative, it ends when the counter falls below the end value. Nested FORNEXT loops are common. Potential issues include off-by-one errors, infinite loops if the end condition is never reached, and differences in how floating-point counters are handled across dialects.

Applications typically include performing repeated actions a known number of times, iterating over array indices, or generating sequences. While FORNEXT is most associated with BASIC, its core concept appears in many languages under the for loop family, sometimes with different syntax or naming.

See also: loop constructs, while loop, do-while loop.