班费收支管理系统代码有1.自行输入班费收入或支出的日期，来源，金额，2.班费信息的修改，3.按班费支出或收入的日期查询班费信息，4.班费信息展示并计算班费余额。请用c语言实现

好的，以下是班费收支管理系统的 C 语言实现：

#include <stdio.h>
#include <string.h>

#define MAX_RECORDS 100

struct Record {
    char date[20];
    char source[50];
    float amount;
};

struct ClassFee {
    struct Record records[MAX_RECORDS];
    int count;
    float balance;
};

void add_income(struct ClassFee *cf, char date[], char source[], float amount) {
    strcpy(cf->records[cf->count].date, date);
    strcpy(cf->records[cf->count].source, source);
    cf->records[cf->count].amount = amount;
    cf->balance += amount;
    cf->count++;
}

void add_expense(struct ClassFee *cf, char date[], char source[], float amount) {
    strcpy(cf->records[cf->count].date, date);
    strcpy(cf->records[cf->count].source, source);
    cf->records[cf->count].amount = -amount;
    cf->balance -= amount;
    cf->count++;
}

void modify_info(struct ClassFee *cf, int idx, char date[], char source[], float amount) {
    cf->balance -= cf->records[idx].amount;
    strcpy(cf->records[idx].date, date);
    strcpy(cf->records[idx].source, source);
    cf->records[idx].amount = amount;
    cf->balance += amount;
}

void search_info(struct ClassFee *cf, char date[]) {
    printf("日期\t来源\t金额\n");
    for (int i = 0; i < cf->count; i++) {
        if (strcmp(cf->records[i].date, date) == 0) {
            printf("%s\t%s\t%.2f\n", cf->records[i].date, cf->records[i].source, cf->records[i].amount);
        }
    }
}

void show_info(struct ClassFee *cf) {
    printf("日期\t来源\t金额\n");
    for (int i = 0; i < cf->count; i++) {
        printf("%s\t%s\t%.2f\n", cf->records[i].date, cf->records[i].source, cf->records[i].amount);
    }
    printf("班费余额：%.2f\n", cf->balance);
}

int main() {
    struct ClassFee cf = {0};
    add_income(&cf, "2022-01-01", "班费收入", 1000);
    add_expense(&cf, "2022-01-03", "购买文具", 200);
    add_expense(&cf, "2022-01-05", "场地租赁", 500);
    show_info(&cf);
    modify_info(&cf, 1, "2022-01-04", "购买文具", 300);
    show_info(&cf);
    search_info(&cf, "2022-01-03");
    return 0;
}

以上代码实现了班费收支管理系统的基本功能，包括添加收入/支出、修改信息、查询信息和展示信息，并且可以计算出班费余额。需要注意的是，以上代码仅供参考，具体实现方法可以根据实际需求进行调整。