我的程序主要是询问用户输入，并将登录数据、用户名等数据保存在文本文件中，并使用同一文件检索数据并显示在输出控制台中。程序执行时，用户可以在选项1到6之间进行选择，选项6用于退出应用程序，其余选项1到5用于用户输入数据和查看文件中存储的数据。
当程序在控制台显示数据时，我看到很多不必要的 ASCii 代码。为什么它会出现，我该如何让它们消失？谢谢!!
int main() {
//Considering the max length of data entered (name) to be 15.
char data[15];
int n = 0, option = 0, count_n = 0;
//This is the initial mark alloted to a subject.
string empty = "00";
string proctor = "";
//Name of the file in which DB is stored.
ifstream f("Example.txt");
string line;
//The following for loop counts the total number of lines in the file.
for (int i = 0; std::getline(f, line); ++i) {
count_n++;
}
while (option != 6) {
//This prints out all the available options in the DB
cout << "\nAvailable operations: \n1. Add New Students\n2."
<< "Student Login\n3. Faculty Login\n4. Proctor Login\n5. Admin View\n"
<< "6. Exit\nEnter option: ";
cin >> option;
if (option == 1) {
cout << "Enter the number of students: ";
cin >> n;
count_n = count_n + n;
for (int i = 0; i < n; i++) {
ofstream outfile;
outfile.open("Example.txt", ios::app);
//The entire data of a single student is stored line-by-line.
cout << "Enter your registration number: ";
cin >> data;
outfile << data << "\t";
cout << "Enter your name: ";
cin >> data;
int len = strlen(data);
while (len < 15) {
data[len] = ' ';
len = len + 1;
}
outfile << data << "\t";
//Inserting empty data initially into the file
outfile << empty << "\t";
outfile << empty << "\t";
cout << "\b \b";
cout << "Enter your proctor ID: ";
cin >> proctor;
outfile << proctor << endl;
}
}
else if (option == 2) {
char regno[9];
cout << "Enter your registration number: ";
cin >> regno;
ifstream infile;
int check = 0;
infile.open("Example.txt", ios::in);
//This loop prints out the data according to the registration number specified.
while (infile >> data) {
if (strcmp(data, regno) == 0) {
cout << "\nRegistration Number: " << data << endl;
infile >> data;
cout << "Name: " << data << endl;
infile >> data;
cout << "CSE1001 mark: " << data << endl;
infile >> data;
cout << "CSE1002 mark: " << data << endl;
infile >> data;
cout << "Proctor ID: " << data << endl;
infile.close();
check = 1;
}
}
if (check == 0) {
cout << "No such registration number found!" << endl;
}
}
//This loop is used to view and add marks to the database of a student.
else if (option == 3) {
char subcode[7];
cout << "Enter your subject code: ";
cin >> subcode;
string code1 = "CSE1001", code2 = "CSE1002", mark = "";
ifstream infile;
int check = 0;
cout << "\nAvailable operations: \n1. Add data about marks\n"
<< "2. View data\nEnter option: ";
cin >> option;
if (option == 1) {
cout << "Warning! You would need to add mark"
<< "details for all the students!" << endl;
for (int i = 0; i < count_n; i++) {
fstream file("Example.txt");
//The seek in file has been done according to the length
//of the data being inserted. It needs to adjusted accordingly
//for diffferent lengths of data.
if (strcmp(subcode, code1.c_str()) == 0) {
file.seekp(26 + 37 * i, std::ios_base::beg);
cout << "Enter the mark of student#" << (i + 1) << " : ";
cin >> mark;
file.write(mark.c_str(), 2);
}
if (strcmp(subcode, code2.c_str()) == 0) {
file.seekp(29 + 37 * i, std::ios_base::beg);
cout << "Enter the mark of student#" << (i + 1) << " : ";
cin >> mark;
file.write(mark.c_str(), 2);
}
}
}
//This loop is used to view marks of a student.
//The extra infile commands have been used to get a specific mark
//only since the data has been seperated by a tabspace.
else if (option == 2) {
infile.open("Example.txt", ios::in);
if (strcmp(subcode, code1.c_str()) == 0) {
cout << "Registration number - Marks\n" << endl;
while (infile >> data) {
cout << data;
infile >> data;
infile >> data;
cout << " - " << data << endl;
infile >> data;
infile >> data;
check = 1;
}
}
infile.close();
infile.open("Example.txt", ios::in);
if (strcmp(subcode, code2.c_str()) == 0) {
cout << "Registration number - Marks\n" << endl;
while (infile >> data) {
cout << data;
infile >> data;
infile >> data;
infile >> data;
cout << " - " << data << endl;
infile >> data;
check = 1;
}
}
}
infile.close();
if (check == 0) {
cout << "No such subject code found!" << endl;
}
}
//This loop displays all the details of students under the same proctor ID.
else if (option == 4) {
char procid[7];
cout << "Enter your proctor ID: ";
cin >> procid;
int check = 1;
char temp1[100], temp2[100], temp3[100];
char temp4[100], id[100];
ifstream infile;
infile.open("Example.txt", ios::in);
while (infile >> temp1) {
infile >> temp2;
infile >> temp3;
infile >> temp4;
infile >> id;
if (strcmp(id, procid) == 0) {
cout << "\nRegistration Number: " << temp1 << endl;
cout << "Name: " << temp2 << endl;
cout << "CSE1001 Mark: " << temp3 << endl;
cout << "CSE1002 Mark: " << temp4 << endl;
check = 1;
}
}
if (check == 0) {
cout << "No such proctor ID found!" << endl;
}
}
//This loop acts as an admin view to see all the data in the file.
else if (option == 5) {
char password[25];
cout << "Enter the admin password: ";
cin >> password;
//This variable value can be changed according to your requirement
//of the administrator password.
string admin_pass = "admin";
if (strcmp(password, admin_pass.c_str()) == 0) {
cout << "Reg No. \tName\tCSE1001\tCSE1002\tProctor ID" << endl;
ifstream infile;
infile.open("Example.txt", ios::in);
char data[20];
while (infile >> data) {
cout << data << "\t";
infile >> data;
cout << data << "\t";
infile >> data;
cout << data << "\t";
infile >> data;
cout << data << "\t";
infile >> data;
cout << data << endl;
}
}
}
}
}
这是输出:
最佳答案
╠ 字符是一个 box drawing character .在代码页 437它由十六进制值 0xCC 表示.
在本例中它是一个 magic hex value这意味着它是未初始化的堆栈内存。
data array 有 20 个字符长，但它会退化为一个指针和 operator<<输出字符，直到它得到一个空字符。所以在这种情况下，很多未初始化的内存╠字符直到\0在内存中找到字符。
似乎是未初始化的data变量在上一次运行时写入文件，现在按原样读回。如果读取不成功，它可能会放置一个 \0。在 data 的第一个位置char数组，在那种情况下不会有输出。
我用一个空的输入文件运行程序并添加了一个学生。这存储在文本文件中(使用 Visual Studio 的文本编辑器查看):
REGNUM123 Pete ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌ 00 00 PROC432
在这种情况下 Ì , 或带有严肃字符的拉丁文大写字母 i 是 0xCC Unicode and multiple other encodings 中的十六进制值.添加学生时，写入的字符数不一定等于 data 中的字符数。数组(在这种情况下为 15)。它们一直写到 \0找到了。
关于c++ - 我的程序控制台输出中出现未知的 ascii 代码字符，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50117087/