A sequence of statements becomes a "group" when preceded by a codice_4 statement and followed by an codice_15 statement. Groups may include nested groups and begin blocks. The codice_16 statement specifies a group or a single statement as the codice_17 part and the codice_18 part (see the sample program). The group is the unit of iteration. The begin "block" (codice_19) may contain declarations for names and internal procedures local to the block. A "procedure" starts with a codice_11 statement and is terminated syntactically by an codice_15 statement. The body of a procedure is a sequence of blocks, groups, and statements and contains declarations for names and procedures local to the procedure or codice_22 to the procedure.