18 real w(4, 4) write(*,小)请输入一个4×4的矩阵 read(,)(W(]j)=1,4),=1,4) call sum w, X1, X2) write(*,水)主对角线元素之和=,x1 Wite(,水)次对角线元素之和=,x2 end §2子例程子程序 2021/2/2418 2021/2/24 §2 子例程子程序 real w(4,4) write(* , *)'请输入一个4×4的矩阵:' read(* , *)( (w(i,j),j=1,4) ,i=1,4) call sum(w, x1, x2) write(* , *)'主对角线元素之和=', x1 write(* , *)'次对角线元素之和=', x2 end