commit 0baf07a5974a3f0b1ee8cc759cdd3188b5b81ed7
Author: lzy <lllzzzyyy@buaa.edu.cn>
Date:   Sun Mar 10 16:11:35 2024 +0800

    Initial commit

diff --git a/Chapter1/Section2/hello b/Chapter1/Section2/hello
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diff --git a/Chapter1/Section2/hello.c b/Chapter1/Section2/hello.c
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--- /dev/null
+++ b/Chapter1/Section2/hello.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#if 0
+void main(void);
+void main(int argc, char **argv);// char *argv[]
+int main(int argc, char **argv);
+int main(void);
+#endif
+
+int main(void)
+{
+    printf("Hello world!\n");
+
+    exit(0);
+}
diff --git a/Chapter1/Section3/a b/Chapter1/Section3/a
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diff --git a/Chapter1/Section3/a.c b/Chapter1/Section3/a.c
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--- /dev/null
+++ b/Chapter1/Section3/a.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+
+int main()
+{
+    FILE *fp;
+
+    fp = fopen("tmp", "r");
+    if (fp == NULL)
+    {
+        fprintf(stderr, "fopen():%s\n", strerror(errno));
+        exit(1);
+    }
+    puts("ok!");
+    exit(0);
+}
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diff --git a/Chapter1/Section3/a.out b/Chapter1/Section3/a.out
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diff --git a/Chapter1/Section3/hello b/Chapter1/Section3/hello
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diff --git a/Chapter1/Section3/hello.c b/Chapter1/Section3/hello.c
new file mode 100644
index 0000000..e4b8681
--- /dev/null
+++ b/Chapter1/Section3/hello.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main(void)
+{
+    int *p = NULL;
+    int i;
+    p = (int *)malloc(sizeof(int));
+    if (p == NULL)
+        return -1;
+    printf("Hello world!\n");
+    return 0;
+}
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diff --git a/Chapter1/Section3/return b/Chapter1/Section3/return
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diff --git a/Chapter1/Section3/return.c b/Chapter1/Section3/return.c
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--- /dev/null
+++ b/Chapter1/Section3/return.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+int main(void)
+{
+    printf("Hello world!\n");
+}
diff --git a/Chapter2/Section2/bool b/Chapter2/Section2/bool
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diff --git a/Chapter2/Section2/bool.c b/Chapter2/Section2/bool.c
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index 0000000..b2b9f01
--- /dev/null
+++ b/Chapter2/Section2/bool.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+int main()
+{
+    bool a = false;
+    printf("a = %d\n", a);
+    exit(0);
+}
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diff --git a/Chapter2/Section2/float.c b/Chapter2/Section2/float.c
new file mode 100644
index 0000000..410439e
--- /dev/null
+++ b/Chapter2/Section2/float.c
@@ -0,0 +1,10 @@
+int func(float f)
+{
+    if (f < 0)
+        return -1;
+    // else if (f == 0)
+    else if (fabs(f - 0) <= 1e-6)
+        return 0;
+    else
+        return 1;
+}
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diff --git a/Chapter2/Section4/define b/Chapter2/Section4/define
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diff --git a/Chapter2/Section4/define.c b/Chapter2/Section4/define.c
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--- /dev/null
+++ b/Chapter2/Section4/define.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define PI 3.14
+#define ADD 2 + 3
+#define ADD1 (2 + 3)
+
+#define MAX(a, b) (a > b ? a : b)
+#define MAX1(a, b) ((a) > (b) ? (a) : (b))
+
+#define MAX2(a, b)               \
+    ({                           \
+        int A = a, B = b;        \
+        ((A) > (B) ? (A) : (B)); \
+    })
+
+#define MAX3(a, b)               \
+    ({                           \
+        typeof(a) A = a, B = b;  \
+        ((A) > (B) ? (A) : (B)); \
+    })
+
+int max(int a, int b)
+{
+    return a > b ? a : b;
+}
+
+int main()
+{
+    // printf("%d\n", ADD * ADD);
+    // 相当于 2+3*2+3
+    // 故输出11而不是25
+    // printf("%d\n", ADD1 * ADD1);
+    // 相当于(2+3)*(2+3)
+    // 正常输出25
+
+    int i = 5, j = 3;
+    // printf("%d\n", MAX(i, j));
+    // 输出5
+
+    // printf("%d\n", MAX(i, j * 2));
+    // 输出6
+
+    // printf("i=%d\tj=%d\n", i, j);
+    // printf("%d\n", MAX1(i++, j++));
+    // printf("i=%d\tj=%d\n", i, j);
+    // 输出：
+    // i = 5 j = 3
+    // 6
+    // i = 7 j = 4
+    // 为什么i自增了两次？
+    // 预处理结果
+    // printf("%d\n", ((i++) + (j++) ? (i++) : (j++)));
+
+    printf("i=%d\tj=%d\n", i, j);
+    printf("%d\n", MAX2(i++, j++));
+    printf("i=%d\tj=%d\n", i, j);
+
+    exit(0);
+}
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