why the program doesn't read my scanf and skip and jump to the next printf?

****/ 104 - /**** 105 //student 2 details 106 *** 107 108 //students ID: promt (Instruction) 109 printf("Please Enter Student ID 2: "); 110 //Student ID: Read from keyboard 111 scanf("%c_%c %d", &id_1, &id_2, &id_3); 112 //Check Student ID 113 printf("Student ID 2 is: %c%c%d ", id_1, id_2, id_3); 114 115 printf("Enter Student class:"); 116 117 scanf("%d", &clss); 118 printf("Student class is: %c ", clss); 119 120 /* 121 //BMM1313: Grade & Grade point value 122 123 124 //Grade BMM1313: (Instructions) 125 printf("Enter grade point for BMM1313: "); 126 // Grade BMM1313: Read from keyboard 127 scanf("%lf", &grade_bmm 1313); 128 *** ****/ input Please Enter Student ID 1: ma23456 Student ID 2 is: ma23456 Enter Student 2 Class: 1 Student Class is: Enter grade point for BMM1313: 4 Enter grade point for BMM1001: 4 Enter grade point for BMM1011: 4 Enter grade point for BMM1821: 4 Please Enter Student ID 2: ma12345 Student ID 2 is: m23456 Enter Student Class:Student class is: Enter grade point for BMM1313: Enter grade point for BMM1001: Enter grade point for BMM1011: Enter grade point for BMM 1821. Please Enter Student ID 3: Enter Student Class: |