struct srt{int num;char nm[8];float xy;}aa;
应该是4+4+4，=12
这个就要看编译器了，不同编译器里，int的长度不一样的。
看看这个，对结构体存储方式进行了说明：https://blog.csdn.net/qq_43516928/article/details/119680760?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165208961016781432925190%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=165208961016781432925190&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_ecpm_v1~rank_v31_ecpm-1-119680760-null-null.nonecase&utm_term=%E6%95%B0%E6%8D%AE%E5%AF%B9%E5%85%B6&spm=1018.2226.3001.4450