3.2.1程序解析例3-5输入一个形式如“操作数运算符操作数”的四则运#include<stdio.h>算表达式，输出运算结果。int main(void)double value1, value2;charop;printf("Typeinanexpression:");scanf("%if%c%lf"&value1,&op,&value2);if(op == '+)printf("=%.2fln",value1 + value2);elseif(op=='-)Type in an expression: 3.1+4.8printf("=%.2fin", value1 - value2);=7.90elseif(op ==**")printf("=%.2fin", value1 * value2);elseif(op==')printf("=%.2fin", value1 / value2);ielseprintf("Unknown operatorln");return o;
3.2.1 程序解析 # include <stdio.h> int main(void) { double value1, value2; char op; printf("Type in an expression: "); scanf("%lf%c%lf", &value1, &op, &value2); if(op == '+') printf("=%.2f\n", value1 + value2); else if(op == '-') printf("=%.2f\n", value1 - value2); else if(op == '*') printf("=%.2f\n", value1 * value2); else if(op == '/') printf("=%.2f\n", value1 / value2); else printf("Unknown operator\n"); return 0; } 例3-5 输入一个形式如“操作 数 运算符 操作数”的四则运 算表达式，输出运算结果。 Type in an expression: 3.1+4.8 =7.90
3.2.2字符类型char为类型名称；char op;op为char类型变量(op =='+')(op == "-")字符型数据字符变量：op口字符常量：‘+*
3.2.2 字符类型 ( op == '+' ) ( op == '-' ) 字符型数据 字符变量：op 字符常量： '+' '-' '*' '/' char为类型名称； op为char类型变量 char op;
字符常量'a'‘z'‘A'‘Z'"o'"g'"n'ASCII字符集：列出所有可用的字符每个字符：惟一的次序值（ASCI码）ASCII码表符号符号10 进制符号10 进制符号10进制10进制'0'-'9'P80112@6496PQ81q1136597A'A'-Z'R82114HB6698bs83115067C99'a'-'z'T84x116D68d100D851174E69101e486118470f102FW87w119G71103g区分数字1和X88120x72Hh104Y89121y13Ii105数字字符"1'290122N74J106J[91123375Kk10719212476L1108193112577M109I94126Nto110n095127111079
'a' 'z' 'A' 'Z' '0' '9' ' ' '\n' 字符常量 ASCII字符集：列出所有可用的字符 每个字符：惟一的次序值（ ASCII 码） '0'-'9' 'A'-'Z' 'a'-'z' 区分数字 1 和 数字字符 '1