请使用BASIC或者QBASIC语言的循环结构编写程序

Question

1.实现将100元人民币换成1,2,5,10,50元的兑换方法,要求每种兑换方法中,每种面值至少有一张.
2.编写一程序.要求:随机产生20个字符,每产生一个即显示在屏幕上,练习者通过键盘输入该字符,对了继续产生新字符,错了再次输入,直至正确.
3.在屏幕上用"*"画出一条正弦曲线.
4.歌德巴赫猜想.任意一个大于或等于4的偶数总能表示成两个素数之和.
还有其他答案吗?

急啊!

Answer 1

(1) CLS
FOR i = 1 TO 2
FOR j = 1 TO 10
FOR k = 1 TO 20
FOR l = 1 TO 50
FOR m = 1 TO 100
IF i * 50 + j * 10 + k * 5 + l * 2 + m = 100 AND i <> 0 AND j <> 0 AND k <> 0 AND l <> 0 AND m <> 0 THEN
PRINT "1:"; m
PRINT "2:"; l
PRINT "5:"; k
PRINT "10:"; j
PRINT "50:"; i
END
END IF
NEXT m
NEXT l
NEXT k
NEXT j
NEXT i

(2)CLS
RANDOMIZE TIMER
FOR i = 1 TO 20
a = INT(RND * 26 + 65)
a$ = CHR$(a)
PRINT a$
DO
INPUT b$
b = ASC(b$)
LOOP UNTIL a = b
NEXT i

(3)不在明白

(4)CLS
DO
INPUT n
LOOP UNTIL n MOD 2 = 0 AND n >= 4
DO
i = i + 1
j = n - i
f = 0
FOR k = 1 TO i - 1
IF i MOD k = 0 THEN f = f + 1
NEXT k
IF f = 1 THEN
f = 0
FOR k = 1 TO j - 1
IF j MOD k = 0 THEN f = f + 1
NEXT k
IF f = 1 THEN PRINT n; "="; i; "+"; j: END
END IF
LOOP

Answer 2

1)for i=1 to 50
for k=1 to 25
for l=1 to 10
for o=1 to 5
if i+(k*2)+(l*5)+(o*10)+50=100 then print i,k,l,o,1
next o,l,k,i

2)CLS
RANDOMIZE TIMER
FOR I=1 TO 20
A=(INT(RND* 68)+33)
1 INPUT B$
B=ASC(B$)
IF B<>A THEN GOTO 1
NEXT I

3)不明白

4)input n
for i=1 to n
for j=1 to n
if i+j=n then
for k=2 to i-1
if i mod k=0 then 1
next k
for l=2 to j-1
if j mod l=0 then 1
next l
print n;"=";i;"=";j
end if
1 next j,i