Hi!

>>
But I use vf5.0 ,Could you give me some advice?
<<

No idea - I tested also in Visual FoxPro 05.00.00.0415 for Windows - no problem:

SET DECI to 2
local v1,v2,v3,v4,v5,v6,v7,v8,v9,v10,v11,v12,v13,v14,v15,v16,v17,v18,v19,v20
store 0 to v1,v2,v3,v4,v5,v6,v7,v8,v9,v10,v11,v12,v13,v14,v15,v16,v17,v18,v19,v20
v20=v1+v2+v3+v4+v5+v6+v7+v8+v9+v10+v11+v12+v13+v14+v15+v16+v17+v18+v19
? STR(v20,30,18)