Objective

Declare the four fields of record in the order that brings sizeof(record) down to 16 bytes, then implement the accessors Grademe uses to read them back.

Steps

• Write record.h and record.c. The header defines the type, the source file implements the functions.
• record holds exactly four fields, with these names and these types: long stamp, int id, short code, unsigned char flag.
• The order of those four fields is your call, and it is the only thing that moves the size. The starter declares id before stamp and pays 24 bytes for it.
• The four fields carry 15 bytes of data. A layout that costs 16 bytes wastes one padding byte, and that is the target.
• Each field lands at an offset that is a multiple of its own width, and the compiler inserts padding to get it there. Order the fields so it has almost nothing left to insert.
• Grademe also reads _Alignof(record), which the widest field sets to 8, and it checks that no two fields share a byte.
• Guard record.h: Grademe includes it twice in the same translation unit. A header that defines a struct body without an #ifndef RECORD_H / #define RECORD_H / #endif guard fails to compile the second time.
• Declare all five prototypes in record.h: void record_set(record *dst, long stamp, int id, short code, unsigned char flag);, long record_stamp(const record *src);, int record_id(const record *src);, short record_code(const record *src);, unsigned char record_flag(const record *src);.
• Keep the const on the four readers. Grademe calls them through a const record *.
• record_set writes its four arguments into *dst and touches nothing else, so no static or global storage sits behind it. Two records filled one after the other keep their own values. Each reader returns one field, unchanged.
• There is no record_size to write. Grademe applies sizeof and offsetof to your own type, so returning 16 from a function of yours proves nothing about the struct.
• Every field keeps the full range of its type: stamp stores LONG_MIN and LONG_MAX, id stores INT_MAX, code stores SHRT_MIN, flag stores 255. Shrinking a field to save space fails those reads.
• record arr[4] must measure exactly four times sizeof(record), so keep it a plain struct: bit-fields and unions break either the size or the round trip.
• No library call is needed anywhere, and record.h needs no #include at all.

Objective

Declare the four fields of record in the order that brings sizeof(record) down to 16 bytes, then implement the accessors Grademe uses to read them back.

Steps

• Write record.h and record.c. The header defines the type, the source file implements the functions.
• record holds exactly four fields, with these names and these types: long stamp, int id, short code, unsigned char flag.
• The order of those four fields is your call, and it is the only thing that moves the size. The starter declares id before stamp and pays 24 bytes for it.
• The four fields carry 15 bytes of data. A layout that costs 16 bytes wastes one padding byte, and that is the target.
• Each field lands at an offset that is a multiple of its own width, and the compiler inserts padding to get it there. Order the fields so it has almost nothing left to insert.
• Grademe also reads _Alignof(record), which the widest field sets to 8, and it checks that no two fields share a byte.
• Guard record.h: Grademe includes it twice in the same translation unit. A header that defines a struct body without an #ifndef RECORD_H / #define RECORD_H / #endif guard fails to compile the second time.
• Declare all five prototypes in record.h: void record_set(record *dst, long stamp, int id, short code, unsigned char flag);, long record_stamp(const record *src);, int record_id(const record *src);, short record_code(const record *src);, unsigned char record_flag(const record *src);.
• Keep the const on the four readers. Grademe calls them through a const record *.
• record_set writes its four arguments into *dst and touches nothing else, so no static or global storage sits behind it. Two records filled one after the other keep their own values. Each reader returns one field, unchanged.
• There is no record_size to write. Grademe applies sizeof and offsetof to your own type, so returning 16 from a function of yours proves nothing about the struct.
• Every field keeps the full range of its type: stamp stores LONG_MIN and LONG_MAX, id stores INT_MAX, code stores SHRT_MIN, flag stores 255. Shrinking a field to save space fails those reads.
• record arr[4] must measure exactly four times sizeof(record), so keep it a plain struct: bit-fields and unions break either the size or the round trip.
• No library call is needed anywhere, and record.h needs no #include at all.